<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>Chapter 9. Internationalization and Localization</title><link rel="stylesheet" href="mysql-html.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.69.1"><link rel="start" href="index.html" title="MySQL 5.0 Reference Manual"><link rel="up" href="index.html" title="MySQL 5.0 Reference Manual"><link rel="prev" href="language-structure.html" title="Chapter 8. Language Structure"><link rel="next" href="data-types.html" title="Chapter 10. Data Types"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 9. Internationalization and Localization</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="language-structure.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="data-types.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="internationalization-localization"></a>Chapter 9. Internationalization and Localization</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="internationalization-localization.html#charset">9.1. Character Set Support</a></span></dt><dd><dl><dt><span class="section"><a href="internationalization-localization.html#charset-general">9.1.1. Character Sets and Collations in General</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-mysql">9.1.2. Character Sets and Collations in MySQL</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-syntax">9.1.3. Specifying Character Sets and Collations</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-connection">9.1.4. Connection Character Sets and Collations</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collations">9.1.5. Collation Issues</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-repertoire">9.1.6. String Repertoire</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-operations">9.1.7. Operations Affected by Character Set Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-unicode">9.1.8. Unicode Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-metadata">9.1.9. UTF-8 for Metadata</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-conversion">9.1.10. Column Character Set Conversion</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-charsets">9.1.11. Character Sets and Collations That MySQL Supports</a></span></dt></dl></dd><dt><span class="section"><a href="internationalization-localization.html#charset-configuration">9.2. The Character Set Used for Data and Sorting</a></span></dt><dd><dl><dt><span class="section"><a href="internationalization-localization.html#german-character-set">9.2.1. Using the German Character Set</a></span></dt></dl></dd><dt><span class="section"><a href="internationalization-localization.html#error-message-language">9.3. Setting the Error Message Language</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#adding-character-set">9.4. Adding a New Character Set</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#character-arrays">9.5. The Character Definition Arrays</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#string-collating">9.6. String Collating Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#multi-byte-characters">9.7. Multi-Byte Character Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#problems-with-character-sets">9.8. Problems With Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#time-zone-support">9.9. MySQL Server Time Zone Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#locale-support">9.10. MySQL Server Locale Support</a></span></dt></dl></div><a class="indexterm" name="id2741492"></a><a class="indexterm" name="id2741501"></a><p>
This chapter covers issues of internationalization (MySQL's
capabilities for adapting to local use) and localization (selecting
particular local conventions):
</p><div class="itemizedlist"><ul type="disc"><li><p>
MySQL support for character sets in SQL statements.
</p></li><li><p>
How to configure the server to support different character sets.
</p></li><li><p>
Selecting the language for error messages.
</p></li><li><p>
How to set the server's time zone and enable per-connection time
zone support.
</p></li><li><p>
Selecting the locale for day and month names.
</p></li></ul></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="charset"></a>9.1. Character Set Support</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-general">9.1.1. Character Sets and Collations in General</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-mysql">9.1.2. Character Sets and Collations in MySQL</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-syntax">9.1.3. Specifying Character Sets and Collations</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-connection">9.1.4. Connection Character Sets and Collations</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collations">9.1.5. Collation Issues</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-repertoire">9.1.6. String Repertoire</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-operations">9.1.7. Operations Affected by Character Set Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-unicode">9.1.8. Unicode Support</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-metadata">9.1.9. UTF-8 for Metadata</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-conversion">9.1.10. Column Character Set Conversion</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-charsets">9.1.11. Character Sets and Collations That MySQL Supports</a></span></dt></dl></div><a class="indexterm" name="id2741566"></a><a class="indexterm" name="id2741575"></a><a class="indexterm" name="id2741584"></a><a class="indexterm" name="id2741593"></a><p>
MySQL includes character set support that enables you to store
data using a variety of character sets and perform comparisons
according to a variety of collations. You can specify character
sets at the server, database, table, and column level. MySQL
supports the use of character sets for the
<code class="literal">MyISAM</code>, <code class="literal">MEMORY</code>,
<code class="literal">NDBCluster</code>, and <code class="literal">InnoDB</code>
storage engines.
</p><p>
This chapter discusses the following topics:
</p><div class="itemizedlist"><ul type="disc"><li><p>
What are character sets and collations?
</p></li><li><p>
The multiple-level default system for character set assignment
</p></li><li><p>
Syntax for specifying character sets and collations
</p></li><li><p>
Affected functions and operations
</p></li><li><p>
Unicode support
</p></li><li><p>
The character sets and collations that are available, with
notes
</p></li></ul></div><p>
Character set issues affect not only data storage, but also
communication between client programs and the MySQL server. If you
want the client program to communicate with the server using a
character set different from the default, you'll need to indicate
which one. For example, to use the <code class="literal">utf8</code> Unicode
character set, issue this statement after connecting to the
server:
</p><pre class="programlisting">SET NAMES 'utf8';
</pre><p>
For more information about character set-related issues in
client/server communication, see
<a href="internationalization-localization.html#charset-connection" title="9.1.4. Connection Character Sets and Collations">Section 9.1.4, “Connection Character Sets and Collations”</a>.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-general"></a>9.1.1. Character Sets and Collations in General</h3></div></div></div><p>
A <em class="firstterm">character set</em> is a set of symbols and
encodings. A <em class="firstterm">collation</em> is a set of rules
for comparing characters in a character set. Let's make the
distinction clear with an example of an imaginary character set.
</p><p>
Suppose that we have an alphabet with four letters:
“<span class="quote"><code class="literal">A</code></span>”,
“<span class="quote"><code class="literal">B</code></span>”,
“<span class="quote"><code class="literal">a</code></span>”,
“<span class="quote"><code class="literal">b</code></span>”. We give each letter a
number: “<span class="quote"><code class="literal">A</code></span>” = 0,
“<span class="quote"><code class="literal">B</code></span>” = 1,
“<span class="quote"><code class="literal">a</code></span>” = 2,
“<span class="quote"><code class="literal">b</code></span>” = 3. The letter
“<span class="quote"><code class="literal">A</code></span>” is a symbol, the number 0 is
the <span class="bold"><strong>encoding</strong></span> for
“<span class="quote"><code class="literal">A</code></span>”, and the combination of all
four letters and their encodings is a
<span class="bold"><strong>character set</strong></span>.
</p><p>
Suppose that we want to compare two string values,
“<span class="quote"><code class="literal">A</code></span>” and
“<span class="quote"><code class="literal">B</code></span>”. The simplest way to do this
is to look at the encodings: 0 for
“<span class="quote"><code class="literal">A</code></span>” and 1 for
“<span class="quote"><code class="literal">B</code></span>”. Because 0 is less than 1,
we say “<span class="quote"><code class="literal">A</code></span>” is less than
“<span class="quote"><code class="literal">B</code></span>”. What we've just done is
apply a collation to our character set. The collation is a set
of rules (only one rule in this case): “<span class="quote">compare the
encodings.</span>” We call this simplest of all possible
collations a <em class="firstterm">binary</em> collation.
</p><p>
But what if we want to say that the lowercase and uppercase
letters are equivalent? Then we would have at least two rules:
(1) treat the lowercase letters
“<span class="quote"><code class="literal">a</code></span>” and
“<span class="quote"><code class="literal">b</code></span>” as equivalent to
“<span class="quote"><code class="literal">A</code></span>” and
“<span class="quote"><code class="literal">B</code></span>”; (2) then compare the
encodings. We call this a
<em class="firstterm">case-insensitive</em> collation. It's a little
more complex than a binary collation.
</p><p>
In real life, most character sets have many characters: not just
“<span class="quote"><code class="literal">A</code></span>” and
“<span class="quote"><code class="literal">B</code></span>” but whole alphabets,
sometimes multiple alphabets or eastern writing systems with
thousands of characters, along with many special symbols and
punctuation marks. Also in real life, most collations have many
rules, not just for whether to distinguish lettercase, but also
for whether to distinguish accents (an “<span class="quote">accent</span>” is
a mark attached to a character as in German
“<span class="quote"><code class="literal">Ö</code></span>”), and for
multiple-character mappings (such as the rule that
“<span class="quote"><code class="literal">Ö</code></span>” =
“<span class="quote"><code class="literal">OE</code></span>” in one of the two German
collations).
</p><p>
MySQL can do these things for you:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Store strings using a variety of character sets
</p></li><li><p>
Compare strings using a variety of collations
</p></li><li><p>
Mix strings with different character sets or collations in
the same server, the same database, or even the same table
</p></li><li><p>
Allow specification of character set and collation at any
level
</p></li></ul></div><p>
In these respects, MySQL is far ahead of most other database
management systems. However, to use these features effectively,
you need to know what character sets and collations are
available, how to change the defaults, and how they affect the
behavior of string operators and functions.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-mysql"></a>9.1.2. Character Sets and Collations in MySQL</h3></div></div></div><p>
The MySQL server can support multiple character sets. To list
the available character sets, use the <code class="literal">SHOW CHARACTER
SET</code> statement. A partial listing follows. For more
complete information, see <a href="internationalization-localization.html#charset-charsets" title="9.1.11. Character Sets and Collations That MySQL Supports">Section 9.1.11, “Character Sets and Collations That MySQL Supports”</a>.
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW CHARACTER SET;</code></strong>
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
...
</pre><p>
Any given character set always has at least one collation. It
may have several collations. To list the collations for a
character set, use the <code class="literal">SHOW COLLATION</code>
statement. For example, to see the collations for the
<code class="literal">latin1</code> (cp1252 West European) character set,
use this statement to find those collation names that begin with
<code class="literal">latin1</code>:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW COLLATION LIKE 'latin1%';</code></strong>
+---------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+---------------------+---------+----+---------+----------+---------+
| latin1_german1_ci | latin1 | 5 | | | 0 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 |
| latin1_danish_ci | latin1 | 15 | | | 0 |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 |
| latin1_bin | latin1 | 47 | | Yes | 1 |
| latin1_general_ci | latin1 | 48 | | | 0 |
| latin1_general_cs | latin1 | 49 | | | 0 |
| latin1_spanish_ci | latin1 | 94 | | | 0 |
+---------------------+---------+----+---------+----------+---------+
</pre><p>
The <code class="literal">latin1</code> collations have the following
meanings:
</p><div class="informaltable"><table border="1"><colgroup><col><col></colgroup><tbody><tr><td><span class="bold"><strong>Collation</strong></span></td><td><span class="bold"><strong>Meaning</strong></span></td></tr><tr><td><code class="literal">latin1_german1_ci</code></td><td>German DIN-1</td></tr><tr><td><code class="literal">latin1_swedish_ci</code></td><td>Swedish/Finnish</td></tr><tr><td><code class="literal">latin1_danish_ci</code></td><td>Danish/Norwegian</td></tr><tr><td><code class="literal">latin1_german2_ci</code></td><td>German DIN-2</td></tr><tr><td><code class="literal">latin1_bin</code></td><td>Binary according to <code class="literal">latin1</code> encoding</td></tr><tr><td><code class="literal">latin1_general_ci</code></td><td>Multilingual (Western European)</td></tr><tr><td><code class="literal">latin1_general_cs</code></td><td>Multilingual (ISO Western European), case sensitive</td></tr><tr><td><code class="literal">latin1_spanish_ci</code></td><td>Modern Spanish</td></tr></tbody></table></div><p>
Collations have these general characteristics:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Two different character sets cannot have the same collation.
</p></li><li><p>
Each character set has one collation that is the
<span class="emphasis"><em>default collation</em></span>. For example, the
default collation for <code class="literal">latin1</code> is
<code class="literal">latin1_swedish_ci</code>. The output for
<code class="literal">SHOW CHARACTER SET</code> indicates which
collation is the default for each displayed character set.
</p></li><li><p>
There is a convention for collation names: They start with
the name of the character set with which they are
associated, they usually include a language name, and they
end with <code class="literal">_ci</code> (case insensitive),
<code class="literal">_cs</code> (case sensitive), or
<code class="literal">_bin</code> (binary).
</p></li></ul></div><p>
In cases where a character set has multiple collations, it might
not be clear which collation is most suitable for a given
application. To avoid choosing the wrong collation, it can be
helpful to perform some comparisons with representative data
values to make sure that a given collation sorts values the way
you expect.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-syntax"></a>9.1.3. Specifying Character Sets and Collations</h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-server">9.1.3.1. Server Character Set and Collation</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-database">9.1.3.2. Database Character Set and Collation</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-table">9.1.3.3. Table Character Set and Collation</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-column">9.1.3.4. Column Character Set and Collation</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-literal">9.1.3.5. Character String Literal Character Set and Collation</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-national">9.1.3.6. National Character Set</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-examples">9.1.3.7. Examples of Character Set and Collation Assignment</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-compatibility">9.1.3.8. Compatibility with Other DBMSs</a></span></dt></dl></div><p>
There are default settings for character sets and collations at
four levels: server, database, table, and column. The
description in the following sections may appear complex, but it
has been found in practice that multiple-level defaulting leads
to natural and obvious results.
</p><p>
<code class="literal">CHARACTER SET</code> is used in clauses that specify
a character set. <code class="literal">CHARSET</code> may be used as a
synonym for <code class="literal">CHARACTER SET</code>.
</p><p>
Character set issues affect not only data storage, but also
communication between client programs and the MySQL server. If
you want the client program to communicate with the server using
a character set different from the default, you'll need to
indicate which one. For example, to use the
<code class="literal">utf8</code> Unicode character set, issue this
statement after connecting to the server:
</p><pre class="programlisting">SET NAMES 'utf8';
</pre><p>
For more information about character set-related issues in
client/server communication, see
<a href="internationalization-localization.html#charset-connection" title="9.1.4. Connection Character Sets and Collations">Section 9.1.4, “Connection Character Sets and Collations”</a>.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-server"></a>9.1.3.1. Server Character Set and Collation</h4></div></div></div><p>
MySQL Server has a server character set and a server
collation. These can be set at server startup on the command
line or in an option file and changed at runtime.
</p><p>
Initially, the server character set and collation depend on
the options that you use when you start
<span><strong class="command">mysqld</strong></span>. You can use
<code class="option">--character-set-server</code> for the character set.
Along with it, you can add <code class="option">--collation-server</code>
for the collation. If you don't specify a character set, that
is the same as saying
<code class="option">--character-set-server=latin1</code>. If you specify
only a character set (for example, <code class="literal">latin1</code>)
but not a collation, that is the same as saying
<code class="option">--character-set-server=latin1</code>
<code class="option">--collation-server=latin1_swedish_ci</code> because
<code class="literal">latin1_swedish_ci</code> is the default collation
for <code class="literal">latin1</code>. Therefore, the following three
commands all have the same effect:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysqld</code></strong>
shell> <strong class="userinput"><code>mysqld --character-set-server=latin1</code></strong>
shell> <strong class="userinput"><code>mysqld --character-set-server=latin1 \</code></strong>
<strong class="userinput"><code>--collation-server=latin1_swedish_ci</code></strong>
</pre><p>
One way to change the settings is by recompiling. If you want
to change the default server character set and collation when
building from sources, use: <code class="option">--with-charset</code>
and <code class="option">--with-collation</code> as arguments for
<span><strong class="command">configure</strong></span>. For example:
</p><pre class="programlisting">shell> <strong class="userinput"><code>./configure --with-charset=latin1</code></strong>
</pre><p>
Or:
</p><pre class="programlisting">shell> <strong class="userinput"><code>./configure --with-charset=latin1 \</code></strong>
<strong class="userinput"><code>--with-collation=latin1_german1_ci</code></strong>
</pre><p>
Both <span><strong class="command">mysqld</strong></span> and
<span><strong class="command">configure</strong></span> verify that the character
set/collation combination is valid. If not, each program
displays an error message and terminates.
</p><p>
The server character set and collation are used as default
values if the database character set and collation are not
specified in <code class="literal">CREATE DATABASE</code> statements.
They have no other purpose.
</p><p>
The current server character set and collation can be
determined from the values of the
<code class="literal">character_set_server</code> and
<code class="literal">collation_server</code> system variables. These
variables can be changed at runtime.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-database"></a>9.1.3.2. Database Character Set and Collation</h4></div></div></div><p>
Every database has a database character set and a database
collation. The <code class="literal">CREATE DATABASE</code> and
<code class="literal">ALTER DATABASE</code> statements have optional
clauses for specifying the database character set and
collation:
</p><pre class="programlisting">CREATE DATABASE <em class="replaceable"><code>db_name</code></em>
[[DEFAULT] CHARACTER SET <em class="replaceable"><code>charset_name</code></em>]
[[DEFAULT] COLLATE <em class="replaceable"><code>collation_name</code></em>]
ALTER DATABASE <em class="replaceable"><code>db_name</code></em>
[[DEFAULT] CHARACTER SET <em class="replaceable"><code>charset_name</code></em>]
[[DEFAULT] COLLATE <em class="replaceable"><code>collation_name</code></em>]
</pre><p>
The keyword <code class="literal">SCHEMA</code> can be used instead of
<code class="literal">DATABASE</code>.
</p><p>
All database options are stored in a text file named
<code class="filename">db.opt</code> that can be found in the database
directory.
</p><p>
The <code class="literal">CHARACTER SET</code> and
<code class="literal">COLLATE</code> clauses make it possible to create
databases with different character sets and collations on the
same MySQL server.
</p><p>
Example:
</p><pre class="programlisting">CREATE DATABASE <em class="replaceable"><code>db_name</code></em> CHARACTER SET latin1 COLLATE latin1_swedish_ci;
</pre><p>
MySQL chooses the database character set and database
collation in the following manner:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If both <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> and
<code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
were specified, then character set
<em class="replaceable"><code>X</code></em> and collation
<em class="replaceable"><code>Y</code></em>.
</p></li><li><p>
If <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> was specified
without <code class="literal">COLLATE</code>, then character set
<em class="replaceable"><code>X</code></em> and its default collation.
</p></li><li><p>
If <code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
was specified without <code class="literal">CHARACTER SET</code>,
then the character set associated with
<em class="replaceable"><code>Y</code></em> and collation
<em class="replaceable"><code>Y</code></em>.
</p></li><li><p>
Otherwise, the server character set and server collation.
</p></li></ul></div><p>
The database character set and collation are used as default
values if the table character set and collation are not
specified in <code class="literal">CREATE TABLE</code> statements. The
database character set also is used by <code class="literal">LOAD DATA
INFILE</code>. The character set and collation have no
other purposes.
</p><p>
The character set and collation for the default database can
be determined from the values of the
<code class="literal">character_set_database</code> and
<code class="literal">collation_database</code> system variables. The
server sets these variables whenever the default database
changes. If there is no default database, the variables have
the same value as the corresponding server-level system
variables, <code class="literal">character_set_server</code> and
<code class="literal">collation_server</code>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-table"></a>9.1.3.3. Table Character Set and Collation</h4></div></div></div><p>
Every table has a table character set and a table collation.
The <code class="literal">CREATE TABLE</code> and <code class="literal">ALTER
TABLE</code> statements have optional clauses for
specifying the table character set and collation:
</p><pre class="programlisting">CREATE TABLE <em class="replaceable"><code>tbl_name</code></em> (<em class="replaceable"><code>column_list</code></em>)
[[DEFAULT] CHARACTER SET <em class="replaceable"><code>charset_name</code></em>] [COLLATE <em class="replaceable"><code>collation_name</code></em>]]
ALTER TABLE <em class="replaceable"><code>tbl_name</code></em>
[[DEFAULT] CHARACTER SET <em class="replaceable"><code>charset_name</code></em>] [COLLATE <em class="replaceable"><code>collation_name</code></em>]
</pre><p>
Example:
</p><pre class="programlisting">CREATE TABLE t1 ( ... ) CHARACTER SET latin1 COLLATE latin1_danish_ci;
</pre><p>
MySQL chooses the table character set and collation in the
following manner:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If both <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> and
<code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
were specified, then character set
<em class="replaceable"><code>X</code></em> and collation
<em class="replaceable"><code>Y</code></em>.
</p></li><li><p>
If <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> was specified
without <code class="literal">COLLATE</code>, then character set
<em class="replaceable"><code>X</code></em> and its default collation.
</p></li><li><p>
If <code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
was specified without <code class="literal">CHARACTER SET</code>,
then the character set associated with
<em class="replaceable"><code>Y</code></em> and collation
<em class="replaceable"><code>Y</code></em>.
</p></li><li><p>
Otherwise, the database character set and collation.
</p></li></ul></div><p>
The table character set and collation are used as default
values if the column character set and collation are not
specified in individual column definitions. The table
character set and collation are MySQL extensions; there are no
such things in standard SQL.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-column"></a>9.1.3.4. Column Character Set and Collation</h4></div></div></div><p>
Every “<span class="quote">character</span>” column (that is, a column of
type <code class="literal">CHAR</code>, <code class="literal">VARCHAR</code>, or
<code class="literal">TEXT</code>) has a column character set and a
column collation. Column definition syntax for <code class="literal">CREATE
TABLE</code> and <code class="literal">ALTER TABLE</code> has
optional clauses for specifying the column character set and
collation:
</p><pre class="programlisting"><em class="replaceable"><code>col_name</code></em> {CHAR | VARCHAR | TEXT} (<em class="replaceable"><code>col_length</code></em>)
[CHARACTER SET <em class="replaceable"><code>charset_name</code></em>] [COLLATE <em class="replaceable"><code>collation_name</code></em>]
</pre><p>
Examples:
</p><pre class="programlisting">CREATE TABLE Table1
(
column1 VARCHAR(5) CHARACTER SET latin1 COLLATE latin1_german1_ci
);
ALTER TABLE Table1 MODIFY
column1 VARCHAR(5) CHARACTER SET latin1 COLLATE latin1_swedish_ci;
</pre><p>
If you convert a column from one character set to another,
<code class="literal">ALTER TABLE</code> attempts to map the data
values, but if the character sets are incompatible, there may
be data loss.
</p><p>
MySQL chooses the column character set and collation in the
following manner:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If both <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> and
<code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
were specified, then character set
<em class="replaceable"><code>X</code></em> and collation
<em class="replaceable"><code>Y</code></em> are used.
</p></li><li><p>
If <code class="literal">CHARACTER SET
<em class="replaceable"><code>X</code></em></code> was specified
without <code class="literal">COLLATE</code>, then character set
<em class="replaceable"><code>X</code></em> and its default collation are
used.
</p></li><li><p>
If <code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
was specified without <code class="literal">CHARACTER SET</code>,
then the character set associated with
<em class="replaceable"><code>Y</code></em> and collation
<em class="replaceable"><code>Y</code></em>.
</p></li><li><p>
Otherwise, the table character set and collation are used.
</p></li></ul></div><p>
The <code class="literal">CHARACTER SET</code> and
<code class="literal">COLLATE</code> clauses are standard SQL.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-literal"></a>9.1.3.5. Character String Literal Character Set and Collation</h4></div></div></div><p>
Every character string literal has a character set and a
collation.
</p><p>
A character string literal may have an optional character set
introducer and <code class="literal">COLLATE</code> clause:
</p><a class="indexterm" name="id2743422"></a><a class="indexterm" name="id2743434"></a><pre class="programlisting">[_<em class="replaceable"><code>charset_name</code></em>]'<em class="replaceable"><code>string</code></em>' [COLLATE <em class="replaceable"><code>collation_name</code></em>]
</pre><p>
Examples:
</p><pre class="programlisting">SELECT '<em class="replaceable"><code>string</code></em>';
SELECT _latin1'<em class="replaceable"><code>string</code></em>';
SELECT _latin1'<em class="replaceable"><code>string</code></em>' COLLATE latin1_danish_ci;
</pre><p>
For the simple statement <code class="literal">SELECT
'<em class="replaceable"><code>string</code></em>'</code>, the string has
the character set and collation defined by the
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> system variables.
</p><p>
The
<code class="literal">_<em class="replaceable"><code>charset_name</code></em></code>
expression is formally called an
<span class="emphasis"><em>introducer</em></span>. It tells the parser,
“<span class="quote">the string that is about to follow uses character set
<em class="replaceable"><code>X</code></em>.</span>” Because this has
confused people in the past, we emphasize that an introducer
does not change the string to the introducer character set
like <a href="functions.html#function_convert"><code class="literal">CONVERT()</code></a> would do. It
does not change the string's value, although padding may
occur. The introducer is just a signal. An introducer is also
legal before standard hex literal and numeric hex literal
notation
(<code class="literal">x'<em class="replaceable"><code>literal</code></em>'</code> and
<code class="literal">0x<em class="replaceable"><code>nnnn</code></em></code>).
</p><p>
Examples:
</p><pre class="programlisting">SELECT _latin1 x'AABBCC';
SELECT _latin1 0xAABBCC;
</pre><p>
MySQL determines a literal's character set and collation in
the following manner:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If both <em class="replaceable"><code>_X</code></em> and <code class="literal">COLLATE
<em class="replaceable"><code>Y</code></em></code> were specified,
then character set <em class="replaceable"><code>X</code></em> and
collation <em class="replaceable"><code>Y</code></em> are used.
</p></li><li><p>
If <em class="replaceable"><code>_X</code></em> is specified but
<code class="literal">COLLATE</code> is not specified, then
character set <em class="replaceable"><code>X</code></em> and its default
collation are used.
</p></li><li><p>
Otherwise, the character set and collation given by the
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> system variables
are used.
</p></li></ul></div><p>
Examples:
</p><div class="itemizedlist"><ul type="disc"><li><p>
A string with <code class="literal">latin1</code> character set and
<code class="literal">latin1_german1_ci</code> collation:
</p><pre class="programlisting">SELECT _latin1'Müller' COLLATE latin1_german1_ci;
</pre></li><li><p>
A string with <code class="literal">latin1</code> character set and
its default collation (that is,
<code class="literal">latin1_swedish_ci</code>):
</p><pre class="programlisting">SELECT _latin1'Müller';
</pre></li><li><p>
A string with the connection default character set and
collation:
</p><pre class="programlisting">SELECT 'Müller';
</pre></li></ul></div><p>
Character set introducers and the <code class="literal">COLLATE</code>
clause are implemented according to standard SQL
specifications.
</p><p>
An introducer indicates the character set for the following
string, but does not change now how the parser performs escape
processing within the string. Escapes are always interpreted
by the parser according to the character set given by
<code class="literal">character_set_connection</code>.
</p><p>
The following examples show that escape processsing occurs
using <code class="literal">character_set_connection</code> even in the
presence of an introducer. The examples use <code class="literal">SET
NAMES</code> (which changes
<code class="literal">character_set_connection</code>, as discussed in
<a href="internationalization-localization.html#charset-connection" title="9.1.4. Connection Character Sets and Collations">Section 9.1.4, “Connection Character Sets and Collations”</a>), and display the
resulting strings using the
<a href="functions.html#function_hex"><code class="literal">HEX()</code></a> function so that the
exact string contents can be seen.
</p><p>
Example 1:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SET NAMES latin1;</code></strong>
Query OK, 0 rows affected (0.01 sec)
mysql> <strong class="userinput"><code>SELECT HEX('à\n'), HEX(_sjis'à\n');</code></strong>
+------------+-----------------+
| HEX('à\n') | HEX(_sjis'à\n') |
+------------+-----------------+
| E00A | E00A |
+------------+-----------------+
1 row in set (0.00 sec)
</pre><p>
Here, “<span class="quote"><code class="literal">à</code></span>” (hex value
<code class="literal">E0</code>) is followed by
“<span class="quote"><code class="literal">\n</code></span>”, the escape sequence for
newline. The escape sequence is interpreted using the
<code class="literal">character_set_connection</code> value of
<code class="literal">latin1</code> to produce a literal newline (hex
value <code class="literal">0A</code>). This happens even for the second
string. That is, the introducer of <code class="literal">_sjis</code>
does not affect the parser's escape processing.
</p><p>
Example 2:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SET NAMES sjis;</code></strong>
Query OK, 0 rows affected (0.00 sec)
mysql> <strong class="userinput"><code>SELECT HEX('à\n'), HEX(_latin1'à\n');</code></strong>
+------------+-------------------+
| HEX('à\n') | HEX(_latin1'à\n') |
+------------+-------------------+
| E05C6E | E05C6E |
+------------+-------------------+
1 row in set (0.04 sec)
</pre><p>
Here, <code class="literal">character_set_connection</code> is
<code class="literal">sjis</code>, a character set in which the sequence
of “<span class="quote"><code class="literal">à</code></span>” followed by
“<span class="quote"><code class="literal">\</code></span>” (hex values
<code class="literal">05</code> and <code class="literal">5C</code>) is a valid
multi-byte character. Hence, the first two bytes of the string
are interpreted as a single <code class="literal">sjis</code> character,
and the “<span class="quote"><code class="literal">\</code></span>” is not intrepreted
as an escape character. The following
“<span class="quote"><code class="literal">n</code></span>” (hex value
<code class="literal">6E</code>) is not interpreted as part of an escape
sequence. This is true even for the second string; the
introducer of <code class="literal">_latin1</code> does not affect
escape processing.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-national"></a>9.1.3.6. National Character Set</h4></div></div></div><p>
Standard SQL defines <code class="literal">NCHAR</code> or
<code class="literal">NATIONAL CHAR</code> as a way to indicate that a
<code class="literal">CHAR</code> column should use some predefined
character set. MySQL 5.0 uses
<code class="literal">utf8</code> as this predefined character set. For
example, these data type declarations are equivalent:
</p><pre class="programlisting">CHAR(10) CHARACTER SET utf8
NATIONAL CHARACTER(10)
NCHAR(10)
</pre><p>
As are these:
</p><pre class="programlisting">VARCHAR(10) CHARACTER SET utf8
NATIONAL VARCHAR(10)
NCHAR VARCHAR(10)
NATIONAL CHARACTER VARYING(10)
NATIONAL CHAR VARYING(10)
</pre><p>
You can use
<code class="literal">N'<em class="replaceable"><code>literal</code></em>'</code> (or
<code class="literal">n'<em class="replaceable"><code>literal</code></em>'</code>) to
create a string in the national character set. These
statements are equivalent:
</p><pre class="programlisting">SELECT N'some text';
SELECT n'some text';
SELECT _utf8'some text';
</pre><p>
For information on upgrading character sets to MySQL
5.0 from versions prior to 4.1, see the
<em class="citetitle">MySQL 3.23, 4.0, 4.1 Reference Manual</em>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-examples"></a>9.1.3.7. Examples of Character Set and Collation Assignment</h4></div></div></div><p>
The following examples show how MySQL determines default
character set and collation values.
</p><p>
<span class="bold"><strong>Example 1: Table and Column
Definition</strong></span>
</p><pre class="programlisting">CREATE TABLE t1
(
c1 CHAR(10) CHARACTER SET latin1 COLLATE latin1_german1_ci
) DEFAULT CHARACTER SET latin2 COLLATE latin2_bin;
</pre><p>
Here we have a column with a <code class="literal">latin1</code>
character set and a <code class="literal">latin1_german1_ci</code>
collation. The definition is explicit, so that's
straightforward. Notice that there is no problem with storing
a <code class="literal">latin1</code> column in a
<code class="literal">latin2</code> table.
</p><p>
<span class="bold"><strong>Example 2: Table and Column
Definition</strong></span>
</p><pre class="programlisting">CREATE TABLE t1
(
c1 CHAR(10) CHARACTER SET latin1
) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
</pre><p>
This time we have a column with a <code class="literal">latin1</code>
character set and a default collation. Although it might seem
natural, the default collation is not taken from the table
level. Instead, because the default collation for
<code class="literal">latin1</code> is always
<code class="literal">latin1_swedish_ci</code>, column
<code class="literal">c1</code> has a collation of
<code class="literal">latin1_swedish_ci</code> (not
<code class="literal">latin1_danish_ci</code>).
</p><p>
<span class="bold"><strong>Example 3: Table and Column
Definition</strong></span>
</p><pre class="programlisting">CREATE TABLE t1
(
c1 CHAR(10)
) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;
</pre><p>
We have a column with a default character set and a default
collation. In this circumstance, MySQL checks the table level
to determine the column character set and collation.
Consequently, the character set for column
<code class="literal">c1</code> is <code class="literal">latin1</code> and its
collation is <code class="literal">latin1_danish_ci</code>.
</p><p>
<span class="bold"><strong>Example 4: Database, Table, and Column
Definition</strong></span>
</p><pre class="programlisting">CREATE DATABASE d1
DEFAULT CHARACTER SET latin2 COLLATE latin2_czech_ci;
USE d1;
CREATE TABLE t1
(
c1 CHAR(10)
);
</pre><p>
We create a column without specifying its character set and
collation. We're also not specifying a character set and a
collation at the table level. In this circumstance, MySQL
checks the database level to determine the table settings,
which thereafter become the column settings.) Consequently,
the character set for column <code class="literal">c1</code> is
<code class="literal">latin2</code> and its collation is
<code class="literal">latin2_czech_ci</code>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-compatibility"></a>9.1.3.8. Compatibility with Other DBMSs</h4></div></div></div><p>
For MaxDB compatibility these two statements are the same:
</p><pre class="programlisting">CREATE TABLE t1 (f1 CHAR(<em class="replaceable"><code>N</code></em>) UNICODE);
CREATE TABLE t1 (f1 CHAR(<em class="replaceable"><code>N</code></em>) CHARACTER SET ucs2);
</pre></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-connection"></a>9.1.4. Connection Character Sets and Collations</h3></div></div></div><a class="indexterm" name="id2744345"></a><a class="indexterm" name="id2744357"></a><p>
Several character set and collation system variables relate to a
client's interaction with the server. Some of these have been
mentioned in earlier sections:
</p><div class="itemizedlist"><ul type="disc"><li><p>
The server character set and collation can be determined
from the values of the
<code class="literal">character_set_server</code> and
<code class="literal">collation_server</code> system variables.
</p></li><li><p>
The character set and collation of the default database can
be determined from the values of the
<code class="literal">character_set_database</code> and
<code class="literal">collation_database</code> system variables.
</p></li></ul></div><p>
Additional character set and collation system variables are
involved in handling traffic for the connection between a client
and the server. Every client has connection-related character
set and collation system variables.
</p><p>
Consider what a “<span class="quote">connection</span>” is: It's what you make
when you connect to the server. The client sends SQL statements,
such as queries, over the connection to the server. The server
sends responses, such as result sets, over the connection back
to the client. This leads to several questions about character
set and collation handling for client connections, each of which
can be answered in terms of system variables:
</p><div class="itemizedlist"><ul type="disc"><li><p>
What character set is the statement in when it leaves the
client?
</p><p>
The server takes the <code class="literal">character_set_client</code>
system variable to be the character set in which statements
are sent by the client.
</p></li><li><p>
What character set should the server translate a statement
to after receiving it?
</p><p>
For this, the server uses the
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> system variables. It
converts statements sent by the client from
<code class="literal">character_set_client</code> to
<code class="literal">character_set_connection</code> (except for
string literals that have an introducer such as
<code class="literal">_latin1</code> or <code class="literal">_utf8</code>).
<code class="literal">collation_connection</code> is important for
comparisons of literal strings. For comparisons of strings
with column values, <code class="literal">collation_connection</code>
does not matter because columns have their own collation,
which has a higher collation precedence.
</p></li><li><p>
What character set should the server translate to before
shipping result sets or error messages back to the client?
</p><p>
The <code class="literal">character_set_results</code> system variable
indicates the character set in which the server returns
query results to the client. This includes result data such
as column values, and result metadata such as column names.
</p></li></ul></div><p>
You can fine-tune the settings for these variables, or you can
depend on the defaults (in which case, you can skip the rest of
this section).
</p><p>
There are two statements that affect the connection character
sets:
</p><pre class="programlisting">SET NAMES '<em class="replaceable"><code>charset_name</code></em>'
SET CHARACTER SET <em class="replaceable"><code>charset_name</code></em>
</pre><p>
<code class="literal">SET NAMES</code> indicates what character set the
client will use to send SQL statements to the server. Thus,
<code class="literal">SET NAMES 'cp1251'</code> tells the server
“<span class="quote">future incoming messages from this client are in
character set <code class="literal">cp1251</code>.</span>” It also
specifies the character set that the server should use for
sending results back to the client. (For example, it indicates
what character set to use for column values if you use a
<code class="literal">SELECT</code> statement.)
</p><p>
A <code class="literal">SET NAMES '<em class="replaceable"><code>x</code></em>'</code>
statement is equivalent to these three statements:
</p><pre class="programlisting">SET character_set_client = <em class="replaceable"><code>x</code></em>;
SET character_set_results = <em class="replaceable"><code>x</code></em>;
SET character_set_connection = <em class="replaceable"><code>x</code></em>;
</pre><p>
Setting <code class="literal">character_set_connection</code> to
<em class="replaceable"><code>x</code></em> also sets
<code class="literal">collation_connection</code> to the default collation
for <em class="replaceable"><code>x</code></em>. It is not necessary to set
that collation explicitly. To specify a particular collation for
the character sets, use the optional <code class="literal">COLLATE</code>
clause:
</p><pre class="programlisting">SET NAMES '<em class="replaceable"><code>charset_name</code></em>' COLLATE '<em class="replaceable"><code>collation_name</code></em>'
</pre><p>
<code class="literal">SET CHARACTER SET</code> is similar to <code class="literal">SET
NAMES</code> but sets
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> to
<code class="literal">character_set_database</code> and
<code class="literal">collation_database</code>. A <code class="literal">SET CHARACTER
SET <em class="replaceable"><code>x</code></em></code> statement is
equivalent to these three statements:
</p><pre class="programlisting">SET character_set_client = <em class="replaceable"><code>x</code></em>;
SET character_set_results = <em class="replaceable"><code>x</code></em>;
SET collation_connection = @@collation_database;
</pre><p>
Setting <code class="literal">collation_connection</code> also sets
<code class="literal">character_set_connection</code> to the character set
associated with the collation (equivalent to executing
<code class="literal">SET character_set_connection =
@@character_set_database</code>). It is not necessary to set
<code class="literal">character_set_connection</code> explicitly.
</p><p>
When a client connects, it sends to the server the name of the
character set that it wants to use. The server uses the name to
set the <code class="literal">character_set_client</code>,
<code class="literal">character_set_results</code>, and
<code class="literal">character_set_connection</code> system variables. In
effect, the server performs a <code class="literal">SET NAMES</code>
operation using the character set name.
</p><p>
With the <span><strong class="command">mysql</strong></span> client, it is not necessary to
execute <code class="literal">SET NAMES</code> every time you start up if
you want to use a character set different from the default. You
can add the <code class="option">--default-character-set</code> option
setting to your <span><strong class="command">mysql</strong></span> statement line, or in
your option file. For example, the following option file setting
changes the three character set variables set to
<code class="literal">koi8r</code> each time you invoke
<span><strong class="command">mysql</strong></span>:
</p><pre class="programlisting">[mysql]
default-character-set=koi8r
</pre><p>
If you are using the <span><strong class="command">mysql</strong></span> client with
auto-reconnect enabled (which is not recommended), it is
preferable to use the <code class="literal">charset</code> command rather
than <code class="literal">SET NAMES</code>. For example:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>charset utf8</code></strong>
Charset changed
</pre><p>
The <code class="literal">charset</code> command issues a <code class="literal">SET
NAMES</code> statement, and also changes the default
character set that is used if <span><strong class="command">mysql</strong></span>
reconnects after the connection has dropped.
</p><p>
Example: Suppose that <code class="literal">column1</code> is defined as
<code class="literal">CHAR(5) CHARACTER SET latin2</code>. If you do not
say <code class="literal">SET NAMES</code> or <code class="literal">SET CHARACTER
SET</code>, then for <code class="literal">SELECT column1 FROM
t</code>, the server sends back all the values for
<code class="literal">column1</code> using the character set that the
client specified when it connected. On the other hand, if you
say <code class="literal">SET NAMES 'latin1'</code> or <code class="literal">SET
CHARACTER SET latin1</code> before issuing the
<code class="literal">SELECT</code> statement, the server converts the
<code class="literal">latin2</code> values to <code class="literal">latin1</code>
just before sending results back. Conversion may be lossy if
there are characters that are not in both character sets.
</p><p>
If you do not want the server to perform any conversion of
result sets, set <code class="literal">character_set_results</code> to
<code class="literal">NULL</code>:
</p><pre class="programlisting">SET character_set_results = NULL;
</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Currently, UCS-2 cannot be used as a client character set,
which means that <code class="literal">SET NAMES 'ucs2'</code> does not
work.
</p></div><p>
To see the values of the character set and collation system
variables that apply to your connection, use these statements:
</p><pre class="programlisting">SHOW VARIABLES LIKE 'character_set%';
SHOW VARIABLES LIKE 'collation%';
</pre><p>
You must also consider the environment within which your MySQL
application executes. For example, if you will send statements
using UTF-8 test taken from a file that you create in an editor,
you should edit the file with the locale of your environment set
to UTF-8 so that the file's encoding is correct and so that the
operating system handles it correctly. For a script that
executes in a Web environment, the script must handle the
character encoding properly for its interaction with the MySQL
server, and it must generate pages that correctly indicate the
encoding so that browsers know now to display the content of the
pages.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-collations"></a>9.1.5. Collation Issues</h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-collate">9.1.5.1. Using <code class="literal">COLLATE</code> in SQL Statements</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collate-precedence">9.1.5.2. <code class="literal">COLLATE</code> Clause Precedence</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-binary-op">9.1.5.3. <code class="literal">BINARY</code> Operator</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collate-tricky">9.1.5.4. Some Special Cases Where the Collation Determination Is Tricky</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collation-charset">9.1.5.5. Collations Must Be for the Right Character Set</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-collation-effect">9.1.5.6. Examples of the Effect of Collation</a></span></dt></dl></div><p>
The following sections discuss various aspects of character set
collations.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-collate"></a>9.1.5.1. Using <code class="literal">COLLATE</code> in SQL Statements</h4></div></div></div><p>
With the <code class="literal">COLLATE</code> clause, you can override
whatever the default collation is for a comparison.
<code class="literal">COLLATE</code> may be used in various parts of SQL
statements. Here are some examples:
</p><div class="itemizedlist"><ul type="disc"><li><p>
With <code class="literal">ORDER BY</code>:
</p><pre class="programlisting">SELECT k
FROM t1
ORDER BY k COLLATE latin1_german2_ci;
</pre></li><li><p>
With <code class="literal">AS</code>:
</p><pre class="programlisting">SELECT k COLLATE latin1_german2_ci AS k1
FROM t1
ORDER BY k1;
</pre></li><li><p>
With <code class="literal">GROUP BY</code>:
</p><pre class="programlisting">SELECT k
FROM t1
GROUP BY k COLLATE latin1_german2_ci;
</pre></li><li><p>
With aggregate functions:
</p><pre class="programlisting">SELECT MAX(k COLLATE latin1_german2_ci)
FROM t1;
</pre></li><li><p>
With <code class="literal">DISTINCT</code>:
</p><pre class="programlisting">SELECT DISTINCT k COLLATE latin1_german2_ci
FROM t1;
</pre></li><li><p>
With <code class="literal">WHERE</code>:
</p><pre class="programlisting"> SELECT *
FROM t1
WHERE _latin1 'Müller' COLLATE latin1_german2_ci = k;
</pre><pre class="programlisting"> SELECT *
FROM t1
WHERE k LIKE _latin1 'Müller' COLLATE latin1_german2_ci;
</pre></li><li><p>
With <code class="literal">HAVING</code>:
</p><pre class="programlisting">SELECT k
FROM t1
GROUP BY k
HAVING k = _latin1 'Müller' COLLATE latin1_german2_ci;
</pre></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-collate-precedence"></a>9.1.5.2. <code class="literal">COLLATE</code> Clause Precedence</h4></div></div></div><p>
The <code class="literal">COLLATE</code> clause has high precedence
(higher than
<a href="functions.html#operator_or"><code class="literal">||</code></a>),
so the following two expressions are equivalent:
</p><pre class="programlisting">x || y COLLATE z
x || (y COLLATE z)
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-binary-op"></a>9.1.5.3. <code class="literal">BINARY</code> Operator</h4></div></div></div><p>
The <code class="literal">BINARY</code> operator casts the string
following it to a binary string. This is an easy way to force
a comparison to be done byte by byte rather than character by
character. <code class="literal">BINARY</code> also causes trailing
spaces to be significant.
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT 'a' = 'A';</code></strong>
-> 1
mysql> <strong class="userinput"><code>SELECT BINARY 'a' = 'A';</code></strong>
-> 0
mysql> <strong class="userinput"><code>SELECT 'a' = 'a ';</code></strong>
-> 1
mysql> <strong class="userinput"><code>SELECT BINARY 'a' = 'a ';</code></strong>
-> 0
</pre><p>
<code class="literal">BINARY <em class="replaceable"><code>str</code></em></code> is
shorthand for
<a href="functions.html#function_cast"><code class="literal">CAST(<em class="replaceable"><code>str</code></em> AS
BINARY)</code></a>.
</p><p>
The <code class="literal">BINARY</code> attribute in character column
definitions has a different effect. A character column defined
with the <code class="literal">BINARY</code> attribute is assigned the
binary collation of the column's character set. Every
character set has a binary collation. For example, the binary
collation for the <code class="literal">latin1</code> character set is
<code class="literal">latin1_bin</code>, so if the table default
character set is <code class="literal">latin1</code>, these two column
definitions are equivalent:
</p><pre class="programlisting">CHAR(10) BINARY
CHAR(10) CHARACTER SET latin1 COLLATE latin1_bin
</pre><p>
The effect of <code class="literal">BINARY</code> as a column attribute
differs from its effect prior to MySQL 4.1. Formerly,
<code class="literal">BINARY</code> resulted in a column that was
treated as a binary string. A binary string is a string of
bytes that has no character set or collation, which differs
from a non-binary character string that has a binary
collation. For both types of strings, comparisons are based on
the numeric values of the string unit, but for non-binary
strings the unit is the character and some character sets
allow multi-byte characters.
<a href="data-types.html#binary-varbinary" title="10.4.2. The BINARY and VARBINARY Types">Section 10.4.2, “The <code class="literal">BINARY</code> and <code class="literal">VARBINARY</code> Types”</a>.
</p><p>
The use of <code class="literal">CHARACTER SET binary</code> in the
definition of a <code class="literal">CHAR</code>,
<code class="literal">VARCHAR</code>, or <code class="literal">TEXT</code> column
causes the column to be treated as a binary data type. For
example, the following pairs of definitions are equivalent:
</p><pre class="programlisting">CHAR(10) CHARACTER SET binary
BINARY(10)
VARCHAR(10) CHARACTER SET binary
VARBINARY(10)
TEXT CHARACTER SET binary
BLOB
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-collate-tricky"></a>9.1.5.4. Some Special Cases Where the Collation Determination Is Tricky</h4></div></div></div><p>
In the great majority of statements, it is obvious what
collation MySQL uses to resolve a comparison operation. For
example, in the following cases, it should be clear that the
collation is the collation of column <code class="literal">x</code>:
</p><pre class="programlisting">SELECT x FROM T ORDER BY x;
SELECT x FROM T WHERE x = x;
SELECT DISTINCT x FROM T;
</pre><p>
However, when multiple operands are involved, there can be
ambiguity. For example:
</p><pre class="programlisting">SELECT x FROM T WHERE x = 'Y';
</pre><p>
Should this query use the collation of the column
<code class="literal">x</code>, or of the string literal
<code class="literal">'Y'</code>?
</p><p>
Standard SQL resolves such questions using what used to be
called “<span class="quote">coercibility</span>” rules. Basically, this
means: Both <code class="literal">x</code> and <code class="literal">'Y'</code>
have collations, so which collation takes precedence? This can
be difficult to resolve, but the following rules cover most
situations:
</p><div class="itemizedlist"><ul type="disc"><li><p>
An explicit <code class="literal">COLLATE</code> clause has a
coercibility of 0. (Not coercible at all.)
</p></li><li><p>
The concatenation of two strings with different collations
has a coercibility of 1.
</p></li><li><p>
The collation of a column or a stored routine parameter or
local variable has a coercibility of 2.
</p></li><li><p>
A “<span class="quote">system constant</span>” (the string returned by
functions such as <a href="functions.html#function_user"><code class="literal">USER()</code></a>
or <a href="functions.html#function_version"><code class="literal">VERSION()</code></a>) has a
coercibility of 3.
</p></li><li><p>
A literal's collation has a coercibility of 4.
</p></li><li><p>
<code class="literal">NULL</code> or an expression that is derived
from <code class="literal">NULL</code> has a coercibility of 5.
</p></li></ul></div><p>
The preceding coercibility values are current as of MySQL
5.0.3. In MySQL 5.0 prior to 5.0.3, there is no
system constant or ignorable coercibility. Functions such as
<a href="functions.html#function_user"><code class="literal">USER()</code></a> have a coercibility of
2 rather than 3, and literals have a coercibility of 3 rather
than 4.
</p><p>
Those rules resolve ambiguities in the following manner:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Use the collation with the lowest coercibility value.
</p></li><li><p>
If both sides have the same coercibility, then:
</p><div class="itemizedlist"><ul type="circle"><li><p>
If both sides are Unicode, or both sides are not
Unicode, it is an error.
</p></li><li><p>
If one of the sides has a Unicode character set, and
another side has a non-Unicode character set, the side
with Unicode character set wins, and automatic
character set conversion is applied to the non-Unicode
side. For example, the following statement will not
return an error:
</p><pre class="programlisting">SELECT CONCAT(utf8_column, latin1_column) FROM t1;
</pre><p>
It will return a result, and the character set of the
result will be <code class="literal">utf8</code>. The collation
of the result will be the collation of
<code class="literal">utf8_column</code>. Values of
<code class="literal">latin1_column</code> will be automatically
converted to <code class="literal">utf8</code> before
concatenating.
</p></li></ul></div></li></ul></div><p>
Although automatic conversion is not in the SQL standard, the
SQL standard document does say that every character set is (in
terms of supported characters) a “<span class="quote">subset</span>” of
Unicode. Because it is a well-known principle that “<span class="quote">what
applies to a superset can apply to a subset,</span>” we
believe that a collation for Unicode can apply for comparisons
with non-Unicode strings.
</p><p>
Examples:
</p><div class="informaltable"><table border="1"><colgroup><col><col></colgroup><tbody><tr><td><code class="literal">column1 = 'A'</code></td><td>Use collation of <code class="literal">column1</code></td></tr><tr><td><code class="literal">column1 = 'A' COLLATE x</code></td><td>Use collation of <code class="literal">'A' COLLATE x</code></td></tr><tr><td><code class="literal">column1 COLLATE x = 'A' COLLATE y</code></td><td>Error</td></tr></tbody></table></div><p>
The <a href="functions.html#function_coercibility"><code class="literal">COERCIBILITY()</code></a> function
can be used to determine the coercibility of a string
expression:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT COERCIBILITY('A' COLLATE latin1_swedish_ci);</code></strong>
-> 0
mysql> <strong class="userinput"><code>SELECT COERCIBILITY(VERSION());</code></strong>
-> 3
mysql> <strong class="userinput"><code>SELECT COERCIBILITY('A');</code></strong>
-> 4
</pre><p>
See <a href="functions.html#information-functions" title="11.10.3. Information Functions">Section 11.10.3, “Information Functions”</a>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-collation-charset"></a>9.1.5.5. Collations Must Be for the Right Character Set</h4></div></div></div><p>
Each character set has one or more collations, but each
collation is associated with one and only one character set.
Therefore, the following statement causes an error message
because the <code class="literal">latin2_bin</code> collation is not
legal with the <code class="literal">latin1</code> character set:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT _latin1 'x' COLLATE latin2_bin;</code></strong>
ERROR 1253 (42000): COLLATION 'latin2_bin' is not valid
for CHARACTER SET 'latin1'
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-collation-effect"></a>9.1.5.6. Examples of the Effect of Collation</h4></div></div></div><p>
<span class="bold"><strong>Example 1: Sorting German
Umlauts</strong></span>
</p><p>
Suppose that column <code class="literal">X</code> in table
<code class="literal">T</code> has these <code class="literal">latin1</code>
column values:
</p><pre class="programlisting">Muffler
Müller
MX Systems
MySQL
</pre><p>
Suppose also that the column values are retrieved using the
following statement:
</p><pre class="programlisting">SELECT X FROM T ORDER BY X COLLATE <em class="replaceable"><code>collation_name</code></em>;
</pre><p>
The following table shows the resulting order of the values if
we use <code class="literal">ORDER BY</code> with different collations:
</p><div class="informaltable"><table border="1"><colgroup><col><col><col></colgroup><tbody><tr><td><code class="literal">latin1_swedish_ci</code></td><td><code class="literal">latin1_german1_ci</code></td><td><code class="literal">latin1_german2_ci</code></td></tr><tr><td>Muffler</td><td>Muffler</td><td>Müller</td></tr><tr><td>MX Systems</td><td>Müller</td><td>Muffler</td></tr><tr><td>Müller</td><td>MX Systems</td><td>MX Systems</td></tr><tr><td>MySQL</td><td>MySQL</td><td>MySQL</td></tr></tbody></table></div><p>
The character that causes the different sort orders in this
example is the U with two dots over it
(<code class="literal">ü</code>), which the Germans call
“<span class="quote">U-umlaut.</span>”
</p><div class="itemizedlist"><ul type="disc"><li><p>
The first column shows the result of the
<code class="literal">SELECT</code> using the Swedish/Finnish
collating rule, which says that U-umlaut sorts with Y.
</p></li><li><p>
The second column shows the result of the
<code class="literal">SELECT</code> using the German DIN-1 rule,
which says that U-umlaut sorts with U.
</p></li><li><p>
The third column shows the result of the
<code class="literal">SELECT</code> using the German DIN-2 rule,
which says that U-umlaut sorts with UE.
</p></li></ul></div><p>
<span class="bold"><strong>Example 2: Searching for German
Umlauts</strong></span>
</p><p>
Suppose that you have three tables that differ only by the
character set and collation used:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>CREATE TABLE german1 (</code></strong>
-> <strong class="userinput"><code> c CHAR(10)</code></strong>
-> <strong class="userinput"><code>) CHARACTER SET latin1 COLLATE latin1_german1_ci;</code></strong>
mysql> <strong class="userinput"><code>CREATE TABLE german2 (</code></strong>
-> <strong class="userinput"><code> c CHAR(10)</code></strong>
-> <strong class="userinput"><code>) CHARACTER SET latin1 COLLATE latin1_german2_ci;</code></strong>
mysql> <strong class="userinput"><code>CREATE TABLE germanutf8 (</code></strong>
-> <strong class="userinput"><code> c CHAR(10)</code></strong>
-> <strong class="userinput"><code>) CHARACTER SET utf8 COLLATE utf8_unicode_ci;</code></strong>
</pre><p>
Each table contains two records:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>INSERT INTO german1 VALUES ('Bar'), ('Bär');</code></strong>
mysql> <strong class="userinput"><code>INSERT INTO german2 VALUES ('Bar'), ('Bär');</code></strong>
mysql> <strong class="userinput"><code>INSERT INTO germanutf8 VALUES ('Bar'), ('Bär');</code></strong>
</pre><p>
Two of the above collations have an <code class="literal">A = Ä</code>
equality, and one has no such equality
(<code class="literal">latin1_german2_ci</code>). For that reason,
you'll get these results in comparisons:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT * FROM german1 WHERE c = 'Bär';</code></strong>
+------+
| c |
+------+
| Bar |
| Bär |
+------+
mysql> <strong class="userinput"><code>SELECT * FROM german2 WHERE c = 'Bär';</code></strong>
+------+
| c |
+------+
| Bär |
+------+
mysql> <strong class="userinput"><code>SELECT * FROM germanutf8 WHERE c = 'Bär';</code></strong>
+------+
| c |
+------+
| Bar |
| Bär |
+------+
</pre><p>
This is not a bug but rather a consequence of the sorting that
<code class="literal">latin1_german1_ci</code> or
<code class="literal">utf8_unicode_ci</code> do (the sorting shown is
done according to the German DIN 5007 standard).
</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-repertoire"></a>9.1.6. String Repertoire</h3></div></div></div><p>
As of MySQL 5.0.48, string expressions have an attribute known
as <em class="firstterm">repertoire</em>, which can have two values:
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">ASCII</code>: The expression can contain only
characters in the Unicode range <code class="literal">U+0000</code> to
<code class="literal">U+007F</code>.
</p></li><li><p>
<code class="literal">UNICODE</code>: The expression can contain
characters in the Unicode range <code class="literal">U+0000</code> to
<code class="literal">U+FFFF</code>.
</p></li></ul></div><p>
The <code class="literal">ASCII</code> range is a subset of
<code class="literal">UNICODE</code> range, so a string with
<code class="literal">ASCII</code> repertoire can be converted safely
without loss of information to the character set of any string
with <code class="literal">UNICODE</code> repertoire or to a character set
that is a superset of <code class="literal">ASCII</code>. (All MySQL
character sets are supersets of <code class="literal">ASCII</code> with
the exception of <code class="literal">swe7</code>, which reuses some
punctuation characters for Swedish accented characters.) The use
of repertoire enables character set conversion in expressions
for many cases where MySQL would otherwise return an
“<span class="quote">illegal mix of collations</span>” error.
</p><p>
The following discussion provides examples of expressions and
their repertoires, and describes how the use of repertoire
changes string expression evaluation:
</p><div class="itemizedlist"><ul type="disc"><li><p>
The repertoire for string constants depends on string
content:
</p><pre class="programlisting">SET NAMES utf8; SELECT 'abc';
SELECT _utf8'def';
SELECT N'MySQL';
</pre><p>
Although the character set is <code class="literal">utf8</code> in
each of the preceding cases, the strings do not actually
contain any characters outside the ASCII range, so their
repertoire is <code class="literal">ASCII</code> rather than
<code class="literal">UNICODE</code>.
</p></li><li><p>
Columns having the <code class="literal">ascii</code> character set
have <code class="literal">ASCII</code> repertoire because of their
character set. In the following table, <code class="literal">c1</code>
has <code class="literal">ASCII</code> repertoire:
</p><pre class="programlisting">CREATE TABLE t1 (c1 CHAR(1) CHARACTER SET ascii);
</pre><p>
The following example illustrates how repertoire enables a
result to be determined in a case where an error occurs
without repertoire:
</p><pre class="programlisting">CREATE TABLE t1 (
c1 CHAR(1) CHARACTER SET latin1,
c2 CHAR(1) CHARACTER SET ascii
);
INSERT INTO t1 VALUES ('a','b');
SELECT CONCAT(c1,c2) FROM t1;
</pre><p>
Without repertoire, this error occurs:
</p><pre class="programlisting">ERROR 1267 (HY000): Illegal mix of collations (latin1_swedish_ci,IMPLICIT)
and (ascii_general_ci,IMPLICIT) for operation 'concat'
</pre><p>
Using repertoire, subset to superset
(<code class="literal">ascii</code> to <code class="literal">latin1</code>)
conversion can occur and a result is returned:
</p><pre class="programlisting">+---------------+
| CONCAT(c1,c2) |
+---------------+
| ab |
+---------------+
</pre></li><li><p>
Functions with one string argument inherit the repertoire of
their argument. The result of
<a href="functions.html#function_upper"><code class="literal">UPPER(_utf8'<em class="replaceable"><code>abc</code></em>')</code></a>
has <code class="literal">ASCII</code> repertoire, because its
argument has <code class="literal">ASCII</code> repertoire.
</p></li><li><p>
For functions that return a string but do not have string
arguments and use
<code class="literal">character_set_connection</code> as the result
character set, the result repertoire is
<code class="literal">ASCII</code> if
<code class="literal">character_set_connection</code> is
<code class="literal">ascii</code>, and <code class="literal">UNICODE</code>
otherwise:
</p><pre class="programlisting">FORMAT(<em class="replaceable"><code>numeric_column</code></em>, 4);
</pre><p>
Use of repertoire changes how MySQL evaluates the following
example:
</p><pre class="programlisting">SET NAMES ascii;
CREATE TABLE t1 (a INT, b VARCHAR(10) CHARACTER SET latin1);
INSERT INTO t1 VALUES (1,'b');
SELECT CONCAT(FORMAT(a, 4), b) FROM t1;
</pre><p>
Without repertoire, this error occurs:
</p><pre class="programlisting">ERROR 1267 (HY000): Illegal mix of collations (ascii_general_ci,COERCIBLE)
and (latin1_swedish_ci,IMPLICIT) for operation 'concat'
</pre><p>
With repertoire, a result is returned:
</p><pre class="programlisting">+-------------------------+
| CONCAT(FORMAT(a, 4), b) |
+-------------------------+
| 1.0000b |
+-------------------------+
</pre></li><li><p>
Functions with two or more string arguments use the
“<span class="quote">widest</span>” argument repertoire for the result
repertoire (<code class="literal">UNICODE</code> is wider than
<code class="literal">ASCII</code>). Consider the following
<a href="functions.html#function_concat"><code class="literal">CONCAT()</code></a> calls:
</p><pre class="programlisting">CONCAT(_ucs2 0x0041, _ucs2 0x0042)
CONCAT(_ucs2 0x0041, _ucs2 0x00C2)
</pre><p>
For the first call, the repertoire is
<code class="literal">ASCII</code> because both arguments are within
the range of the <code class="literal">ascii</code> character set. For
the second call, the repertoire is
<code class="literal">UNICODE</code> because the second argument is
outside the <code class="literal">ascii</code> character set range.
</p></li><li><p>
The repertoire for function return values is determined
based only on the repertoire of the arguments that affect
the result's character set and collation.
</p><pre class="programlisting">IF(column1 < column2, 'smaller', 'greater')
</pre><p>
The result repertoire is <code class="literal">ASCII</code> because
the two string arguments (the second argument and the third
argument) both have <code class="literal">ASCII</code> repertoire. The
first argument does not matter for the result repertoire,
even if the expression uses string values.
</p></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-operations"></a>9.1.7. Operations Affected by Character Set Support</h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-result">9.1.7.1. Result Strings</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-convert">9.1.7.2. <code class="literal">CONVERT()</code> and
<code class="literal">CAST()</code></a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-show">9.1.7.3. <code class="literal">SHOW</code> Statements and
<code class="literal">INFORMATION_SCHEMA</code></a></span></dt></dl></div><p>
This section describes operations that take character set
information into account.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-result"></a>9.1.7.1. Result Strings</h4></div></div></div><p>
MySQL has many operators and functions that return a string.
This section answers the question: What is the character set
and collation of such a string?
</p><p>
For simple functions that take string input and return a
string result as output, the output's character set and
collation are the same as those of the principal input value.
For example,
<a href="functions.html#function_upper"><code class="literal">UPPER(<em class="replaceable"><code>X</code></em>)</code></a>
returns a string whose character string and collation are the
same as that of <em class="replaceable"><code>X</code></em>. The same applies
for <a href="functions.html#function_instr"><code class="literal">INSTR()</code></a>,
<a href="functions.html#function_lcase"><code class="literal">LCASE()</code></a>,
<a href="functions.html#function_lower"><code class="literal">LOWER()</code></a>,
<a href="functions.html#function_ltrim"><code class="literal">LTRIM()</code></a>,
<a href="functions.html#function_mid"><code class="literal">MID()</code></a>,
<a href="functions.html#function_repeat"><code class="literal">REPEAT()</code></a>,
<a href="functions.html#function_replace"><code class="literal">REPLACE()</code></a>,
<a href="functions.html#function_reverse"><code class="literal">REVERSE()</code></a>,
<a href="functions.html#function_right"><code class="literal">RIGHT()</code></a>,
<a href="functions.html#function_rpad"><code class="literal">RPAD()</code></a>,
<a href="functions.html#function_rtrim"><code class="literal">RTRIM()</code></a>,
<a href="functions.html#function_soundex"><code class="literal">SOUNDEX()</code></a>,
<a href="functions.html#function_substring"><code class="literal">SUBSTRING()</code></a>,
<a href="functions.html#function_trim"><code class="literal">TRIM()</code></a>,
<a href="functions.html#function_ucase"><code class="literal">UCASE()</code></a>, and
<a href="functions.html#function_upper"><code class="literal">UPPER()</code></a>.
</p><p>
Note: The <a href="functions.html#function_replace"><code class="literal">REPLACE()</code></a> function,
unlike all other functions, always ignores the collation of
the string input and performs a case-sensitive comparison.
</p><p>
If a string input or function result is a binary string, the
string has no character set or collation. This can be check by
using the <a href="functions.html#function_charset"><code class="literal">CHARSET()</code></a> and
<a href="functions.html#function_collation"><code class="literal">COLLATION()</code></a> functions, both of
which return <code class="literal">binary</code> to indicate that their
argument is a binary string:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT CHARSET(BINARY 'a'), COLLATION(BINARY 'a');</code></strong>
+---------------------+-----------------------+
| CHARSET(BINARY 'a') | COLLATION(BINARY 'a') |
+---------------------+-----------------------+
| binary | binary |
+---------------------+-----------------------+
</pre><p>
For operations that combine multiple string inputs and return
a single string output, the “<span class="quote">aggregation rules</span>”
of standard SQL apply for determining the collation of the
result:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If an explicit <code class="literal">COLLATE
<em class="replaceable"><code>X</code></em></code> occurs, use
<em class="replaceable"><code>X</code></em>.
</p></li><li><p>
If explicit <code class="literal">COLLATE
<em class="replaceable"><code>X</code></em></code> and
<code class="literal">COLLATE <em class="replaceable"><code>Y</code></em></code>
occur, raise an error.
</p></li><li><p>
Otherwise, if all collations are
<em class="replaceable"><code>X</code></em>, use
<em class="replaceable"><code>X</code></em>.
</p></li><li><p>
Otherwise, the result has no collation.
</p></li></ul></div><p>
For example, with <code class="literal">CASE ... WHEN a THEN b WHEN b THEN
c COLLATE <em class="replaceable"><code>X</code></em> END</code>, the
resulting collation is <em class="replaceable"><code>X</code></em>. The same
applies for <code class="literal">UNION</code>,
<a href="functions.html#operator_or"><code class="literal">||</code></a>,
<a href="functions.html#function_concat"><code class="literal">CONCAT()</code></a>,
<a href="functions.html#function_elt"><code class="literal">ELT()</code></a>,
<a href="functions.html#function_greatest"><code class="literal">GREATEST()</code></a>,
<a href="functions.html#function_if"><code class="literal">IF()</code></a>, and
<a href="functions.html#function_least"><code class="literal">LEAST()</code></a>.
</p><p>
For operations that convert to character data, the character
set and collation of the strings that result from the
operations are defined by the
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> system variables. This
applies only to <a href="functions.html#function_cast"><code class="literal">CAST()</code></a>,
<a href="functions.html#function_conv"><code class="literal">CONV()</code></a>,
<a href="functions.html#function_format"><code class="literal">FORMAT()</code></a>,
<a href="functions.html#function_hex"><code class="literal">HEX()</code></a>,
<a href="functions.html#function_space"><code class="literal">SPACE()</code></a>. Before MySQL 5.0.15,
it also applies to <a href="functions.html#function_char"><code class="literal">CHAR()</code></a>.
</p><p>
If you are uncertain about the character set or collation of
the result returned by a string function, you can use the
<a href="functions.html#function_charset"><code class="literal">CHARSET()</code></a> or
<a href="functions.html#function_collation"><code class="literal">COLLATION()</code></a> function to find
out:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT USER(), CHARSET(USER()), COLLATION(USER());</code></strong>
+----------------+-----------------+-------------------+
| USER() | CHARSET(USER()) | COLLATION(USER()) |
+----------------+-----------------+-------------------+
| test@localhost | utf8 | utf8_general_ci |
+----------------+-----------------+-------------------+
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-convert"></a>9.1.7.2. <a href="functions.html#function_convert"><code class="literal">CONVERT()</code></a> and
<a href="functions.html#function_cast"><code class="literal">CAST()</code></a></h4></div></div></div><p>
<a href="functions.html#function_convert"><code class="literal">CONVERT()</code></a> provides a way to
convert data between different character sets. The syntax is:
</p><pre class="programlisting">CONVERT(<em class="replaceable"><code>expr</code></em> USING <em class="replaceable"><code>transcoding_name</code></em>)
</pre><p>
In MySQL, transcoding names are the same as the corresponding
character set names.
</p><p>
Examples:
</p><pre class="programlisting">SELECT CONVERT(_latin1'Müller' USING utf8);
INSERT INTO utf8table (utf8column)
SELECT CONVERT(latin1field USING utf8) FROM latin1table;
</pre><p>
<a href="functions.html#function_convert"><code class="literal">CONVERT(... USING ...)</code></a> is
implemented according to the standard SQL specification.
</p><p>
You may also use <a href="functions.html#function_cast"><code class="literal">CAST()</code></a> to
convert a string to a different character set. The syntax is:
</p><pre class="programlisting">CAST(<em class="replaceable"><code>character_string</code></em> AS <em class="replaceable"><code>character_data_type</code></em> CHARACTER SET <em class="replaceable"><code>charset_name</code></em>)
</pre><p>
Example:
</p><pre class="programlisting">SELECT CAST(_latin1'test' AS CHAR CHARACTER SET utf8);
</pre><p>
If you use <a href="functions.html#function_cast"><code class="literal">CAST()</code></a> without
specifying <code class="literal">CHARACTER SET</code>, the resulting
character set and collation are defined by the
<code class="literal">character_set_connection</code> and
<code class="literal">collation_connection</code> system variables. If
you use <a href="functions.html#function_cast"><code class="literal">CAST()</code></a> with
<code class="literal">CHARACTER SET X</code>, the resulting character
set and collation are <code class="literal">X</code> and the default
collation of <code class="literal">X</code>.
</p><p>
You may not use a <code class="literal">COLLATE</code> clause inside a
<a href="functions.html#function_cast"><code class="literal">CAST()</code></a>, but you may use it
outside. That is, <a href="functions.html#function_cast"><code class="literal">CAST(... COLLATE
...)</code></a> is illegal, but <a href="functions.html#function_cast"><code class="literal">CAST(...)
COLLATE ...</code></a> is legal.
</p><p>
Example:
</p><pre class="programlisting">SELECT CAST(_latin1'test' AS CHAR CHARACTER SET utf8) COLLATE utf8_bin;
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-show"></a>9.1.7.3. <code class="literal">SHOW</code> Statements and
<code class="literal">INFORMATION_SCHEMA</code></h4></div></div></div><p>
Several <code class="literal">SHOW</code> statements provide additional
character set information. These include <code class="literal">SHOW
CHARACTER SET</code>, <code class="literal">SHOW COLLATION</code>,
<code class="literal">SHOW CREATE DATABASE</code>, <code class="literal">SHOW CREATE
TABLE</code> and <code class="literal">SHOW COLUMNS</code>. These
statements are described here briefly. For more information,
see <a href="sql-syntax.html#show" title="12.5.4. SHOW Syntax">Section 12.5.4, “<code class="literal">SHOW</code> Syntax”</a>.
</p><p>
<code class="literal">INFORMATION_SCHEMA</code> has several tables that
contain information similar to that displayed by the
<code class="literal">SHOW</code> statements. For example, the
<code class="literal">CHARACTER_SETS</code> and
<code class="literal">COLLATIONS</code> tables contain the information
displayed by <code class="literal">SHOW CHARACTER SET</code> and
<code class="literal">SHOW COLLATION</code>.
<a href="information-schema.html" title="Chapter 21. INFORMATION_SCHEMA Tables">Chapter 21, <i><code class="literal">INFORMATION_SCHEMA</code> Tables</i></a>.
</p><p>
The <code class="literal">SHOW CHARACTER SET</code> command shows all
available character sets. It takes an optional
<code class="literal">LIKE</code> clause that indicates which character
set names to match. For example:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW CHARACTER SET LIKE 'latin%';</code></strong>
+---------+-----------------------------+-------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+-----------------------------+-------------------+--------+
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
+---------+-----------------------------+-------------------+--------+
</pre><p>
The output from <code class="literal">SHOW COLLATION</code> includes all
available character sets. It takes an optional
<code class="literal">LIKE</code> clause that indicates which collation
names to match. For example:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW COLLATION LIKE 'latin1%';</code></strong>
+-------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+-------------------+---------+----+---------+----------+---------+
| latin1_german1_ci | latin1 | 5 | | | 0 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 0 |
| latin1_danish_ci | latin1 | 15 | | | 0 |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 |
| latin1_bin | latin1 | 47 | | Yes | 0 |
| latin1_general_ci | latin1 | 48 | | | 0 |
| latin1_general_cs | latin1 | 49 | | | 0 |
| latin1_spanish_ci | latin1 | 94 | | | 0 |
+-------------------+---------+----+---------+----------+---------+
</pre><p>
<code class="literal">SHOW CREATE DATABASE</code> displays the
<code class="literal">CREATE DATABASE</code> statement that creates a
given database:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW CREATE DATABASE test;</code></strong>
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+
</pre><p>
If no <code class="literal">COLLATE</code> clause is shown, the default
collation for the character set applies.
</p><p>
<code class="literal">SHOW CREATE TABLE</code> is similar, but displays
the <code class="literal">CREATE TABLE</code> statement to create a
given table. The column definitions indicate any character set
specifications, and the table options include character set
information.
</p><p>
The <code class="literal">SHOW COLUMNS</code> statement displays the
collations of a table's columns when invoked as <code class="literal">SHOW
FULL COLUMNS</code>. Columns with <code class="literal">CHAR</code>,
<code class="literal">VARCHAR</code>, or <code class="literal">TEXT</code> data
types have collations. Numeric and other non-character types
have no collation (indicated by <code class="literal">NULL</code> as the
<code class="literal">Collation</code> value). For example:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW FULL COLUMNS FROM person\G</code></strong>
*************************** 1. row ***************************
Field: id
Type: smallint(5) unsigned
Collation: NULL
Null: NO
Key: PRI
Default: NULL
Extra: auto_increment
Privileges: select,insert,update,references
Comment:
*************************** 2. row ***************************
Field: name
Type: char(60)
Collation: latin1_swedish_ci
Null: NO
Key:
Default:
Extra:
Privileges: select,insert,update,references
Comment:
</pre><p>
The character set is not part of the display but is implied by
the collation name.
</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-unicode"></a>9.1.8. Unicode Support</h3></div></div></div><p>
MySQL 5.0 supports two character sets for storing
Unicode data:
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">ucs2</code>, the UCS-2 Unicode character set.
</p></li><li><p>
<code class="literal">utf8</code>, the UTF-8 encoding of the Unicode
character set.
</p></li></ul></div><p>
In UCS-2 (binary Unicode representation), every character is
represented by a two-byte Unicode code with the most significant
byte first. For example: <code class="literal">LATIN CAPITAL LETTER
A</code> has the code <code class="literal">0x0041</code> and it is
stored as a two-byte sequence: <code class="literal">0x00 0x41</code>.
<code class="literal">CYRILLIC SMALL LETTER YERU</code> (Unicode
<code class="literal">0x044B</code>) is stored as a two-byte sequence:
<code class="literal">0x04 0x4B</code>. For Unicode characters and their
codes, please refer to the
<a href="http://www.unicode.org/" target="_top">Unicode Home Page</a>.
</p><p>
The MySQL implementation of UCS-2 stores characters in
big-endian byte order and does not use a byte order mark (BOM)
at the beginning of UCS-2 values. Other database systems might
use little-ending byte order or a BOM, in which case conversion
of UCS-2 values will need to be performed when transferring data
between those systems and MySQL.
</p><p>
Currently, UCS-2 cannot be used as a client character set, which
means that <code class="literal">SET NAMES 'ucs2'</code> does not work.
</p><p>
UTF-8 (Unicode Transformation Format with 8-bit units) is an
alternative way to store Unicode data. It is implemented
according to RFC 3629. The idea of UTF-8 is that various Unicode
characters are encoded using byte sequences of different
lengths:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Basic Latin letters, digits, and punctuation signs use one
byte.
</p></li><li><p>
Most European and Middle East script letters fit into a
two-byte sequence: extended Latin letters (with tilde,
macron, acute, grave and other accents), Cyrillic, Greek,
Armenian, Hebrew, Arabic, Syriac, and others.
</p></li><li><p>
Korean, Chinese, and Japanese ideographs use three-byte
sequences.
</p></li></ul></div><p>
RFC 3629 describes encoding sequences that take from one to four
bytes. Currently, MySQL support for UTF-8 does not include
four-byte sequences. (An older standard for UTF-8 encoding is
given by RFC 2279, which describes UTF-8 sequences that take
from one to six bytes. RFC 3629 renders RFC 2279 obsolete; for
this reason, sequences with five and six bytes are no longer
used.)
</p><p>
MySQL uses no BOM for UTF-8 values.
</p><p>
<span class="bold"><strong>Tip</strong></span>: To save space with UTF-8,
use <code class="literal">VARCHAR</code> instead of
<code class="literal">CHAR</code>. Otherwise, MySQL must reserve three
bytes for each character in a <code class="literal">CHAR CHARACTER SET
utf8</code> column because that is the maximum possible
length. For example, MySQL must reserve 30 bytes for a
<code class="literal">CHAR(10) CHARACTER SET utf8</code> column.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-metadata"></a>9.1.9. UTF-8 for Metadata</h3></div></div></div><p>
<em class="firstterm">Metadata</em> is “<span class="quote">the data about the
data.</span>” Anything that <span class="emphasis"><em>describes</em></span> the
database — as opposed to being the
<span class="emphasis"><em>contents</em></span> of the database — is
metadata. Thus column names, database names, usernames, version
names, and most of the string results from
<code class="literal">SHOW</code> are metadata. This is also true of the
contents of tables in <code class="literal">INFORMATION_SCHEMA</code>,
because those tables by definition contain information about
database objects.
</p><p>
Representation of metadata must satisfy these requirements:
</p><div class="itemizedlist"><ul type="disc"><li><p>
All metadata must be in the same character set. Otherwise,
neither the <code class="literal">SHOW</code> commands nor
<code class="literal">SELECT</code> statements for tables in
<code class="literal">INFORMATION_SCHEMA</code> would work properly
because different rows in the same column of the results of
these operations would be in different character sets.
</p></li><li><p>
Metadata must include all characters in all languages.
Otherwise, users would not be able to name columns and
tables using their own languages.
</p></li></ul></div><p>
To satisfy both requirements, MySQL stores metadata in a Unicode
character set, namely UTF-8. This does not cause any disruption
if you never use accented or non-Latin characters. But if you
do, you should be aware that metadata is in UTF-8.
</p><p>
The metadata requirements mean that the return values of the
<a href="functions.html#function_user"><code class="literal">USER()</code></a>,
<a href="functions.html#function_current-user"><code class="literal">CURRENT_USER()</code></a>,
<a href="functions.html#function_session-user"><code class="literal">SESSION_USER()</code></a>,
<a href="functions.html#function_system-user"><code class="literal">SYSTEM_USER()</code></a>,
<a href="functions.html#function_database"><code class="literal">DATABASE()</code></a>, and
<a href="functions.html#function_version"><code class="literal">VERSION()</code></a> functions have the
UTF-8 character set by default.
</p><p>
The server sets the <code class="literal">character_set_system</code>
system variable to the name of the metadata character set:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW VARIABLES LIKE 'character_set_system';</code></strong>
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| character_set_system | utf8 |
+----------------------+-------+
</pre><p>
Storage of metadata using Unicode does <span class="emphasis"><em>not</em></span>
mean that the server returns headers of columns and the results
of <code class="literal">DESCRIBE</code> functions in the
<code class="literal">character_set_system</code> character set by
default. When you use <code class="literal">SELECT column1 FROM t</code>,
the name <code class="literal">column1</code> itself is returned from the
server to the client in the character set determined by the
value of the <code class="literal">character_set_results</code> system
variable, which has a default value of
<code class="literal">latin1</code>. If you want the server to pass
metadata results back in a different character set, use the
<code class="literal">SET NAMES</code> statement to force the server to
perform character set conversion. <code class="literal">SET NAMES</code>
sets the <code class="literal">character_set_results</code> and other
related system variables. (See
<a href="internationalization-localization.html#charset-connection" title="9.1.4. Connection Character Sets and Collations">Section 9.1.4, “Connection Character Sets and Collations”</a>.) Alternatively, a client
program can perform the conversion after receiving the result
from the server. It is more efficient for the client perform the
conversion, but this option is not always available for all
clients.
</p><p>
If <code class="literal">character_set_results</code> is set to
<code class="literal">NULL</code>, no conversion is performed and the
server returns metadata using its original character set (the
set indicated by <code class="literal">character_set_system</code>).
</p><p>
Error messages returned from the server to the client are
converted to the client character set automatically, as with
metadata.
</p><p>
If you are using (for example) the
<a href="functions.html#function_user"><code class="literal">USER()</code></a> function for comparison
or assignment within a single statement, don't worry. MySQL
performs some automatic conversion for you.
</p><pre class="programlisting">SELECT * FROM Table1 WHERE USER() = latin1_column;
</pre><p>
This works because the contents of
<code class="literal">latin1_column</code> are automatically converted to
UTF-8 before the comparison.
</p><pre class="programlisting">INSERT INTO Table1 (latin1_column) SELECT USER();
</pre><p>
This works because the contents of
<a href="functions.html#function_user"><code class="literal">USER()</code></a> are automatically
converted to <code class="literal">latin1</code> before the assignment.
Automatic conversion is not fully implemented yet, but should
work correctly in a later version.
</p><p>
Although automatic conversion is not in the SQL standard, the
SQL standard document does say that every character set is (in
terms of supported characters) a “<span class="quote">subset</span>” of
Unicode. Because it is a well-known principle that “<span class="quote">what
applies to a superset can apply to a subset,</span>” we believe
that a collation for Unicode can apply for comparisons with
non-Unicode strings. For more information about coercion of
strings, see <a href="internationalization-localization.html#charset-collate-tricky" title="9.1.5.4. Some Special Cases Where the Collation Determination Is Tricky">Section 9.1.5.4, “Some Special Cases Where the Collation Determination Is Tricky”</a>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-conversion"></a>9.1.10. Column Character Set Conversion</h3></div></div></div><p>
To convert a binary or non-binary string column to use a
particular character set, use <code class="literal">ALTER TABLE</code>.
For successful conversion to occur, one of the following
conditions must apply:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If the column has a binary data type
(<code class="literal">BINARY</code>, <code class="literal">VARBINARY</code>,
<code class="literal">BLOB</code>), all the values that it contains
must be encoded using a single character set (the character
set you're converting the column to). If you use a binary
column to store information in multiple character sets,
MySQL has no way to know which values use which character
set and cannot convert the data properly.
</p></li><li><p>
If the column has a non-binary data type
(<code class="literal">CHAR</code>, <code class="literal">VARCHAR</code>,
<code class="literal">TEXT</code>), its contents should be encoded in
the column's character set, not some other character set. If
the contents are encoded in a different character set, you
can convert the column to use a binary data type first, and
then to a non-binary column with the desired character set.
</p></li></ul></div><p>
Suppose that a table <code class="literal">t</code> has a binary column
named <code class="literal">col1</code> defined as
<code class="literal">BINARY(50)</code>. Assuming that the information in
the column is encoded using a single character set, you can
convert it to a non-binary column that has that character set.
For example, if <code class="literal">col1</code> contains binary data
representing characters in the <code class="literal">greek</code>
character set, you can convert it as follows:
</p><pre class="programlisting">ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET greek;
</pre><p>
Suppose that table <code class="literal">t</code> has a non-binary column
named <code class="literal">col1</code> defined as <code class="literal">CHAR(50)
CHARACTER SET latin1</code> but you want to convert it to use
<code class="literal">utf8</code> so that you can store values from many
languages. The following statement accomplishes this:
</p><pre class="programlisting">ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET utf8;
</pre><p>
Conversion may be lossy if the column contains characters that
are not in both character sets.
</p><p>
A special case occurs if you have old tables from MySQL 4.0 or
earlier where a non-binary column contains values that actually
are encoded in a character set different from the server's
default character set. For example, an application might have
stored <code class="literal">sjis</code> values in a column, even though
MySQL's default character set was <code class="literal">latin1</code>. It
is possible to convert the column to use the proper character
set but an additional step is required. Suppose that the
server's default character set was <code class="literal">latin1</code> and
<code class="literal">col1</code> is defined as
<code class="literal">CHAR(50)</code> but its contents are
<code class="literal">sjis</code> values. The first step is to convert the
column to a binary data type, which removes the existing
character set information without performing any character
conversion:
</p><pre class="programlisting">ALTER TABLE t MODIFY col1 BINARY(50);
</pre><p>
The next step is to convert the column to a non-binary data type
with the proper character set:
</p><pre class="programlisting">ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET sjis;
</pre><p>
This procedure requires that the table not have been modified
already with statements such as <code class="literal">INSERT</code> or
<code class="literal">UPDATE</code> after an upgrade to MySQL 4.1 or
later. In that case, MySQL would store new values in the column
using <code class="literal">latin1</code>, and the column will contain a
mix of <code class="literal">sjis</code> and <code class="literal">latin1</code>
values and cannot be converted properly.
</p><p>
If you specified attributes when creating a column initially,
you should also specify them when altering the table with
<code class="literal">ALTER TABLE</code>. For example, if you specified
<code class="literal">NOT NULL</code> and an explicit
<code class="literal">DEFAULT</code> value, you should also provide them
in the <code class="literal">ALTER TABLE</code> statement. Otherwise, the
resulting column definition will not include those attributes.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="charset-charsets"></a>9.1.11. Character Sets and Collations That MySQL Supports</h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-unicode-sets">9.1.11.1. Unicode Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-we-sets">9.1.11.2. West European Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-ce-sets">9.1.11.3. Central European Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-se-me-sets">9.1.11.4. South European and Middle East Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-baltic-sets">9.1.11.5. Baltic Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-cyrillic-sets">9.1.11.6. Cyrillic Character Sets</a></span></dt><dt><span class="section"><a href="internationalization-localization.html#charset-asian-sets">9.1.11.7. Asian Character Sets</a></span></dt></dl></div><p>
MySQL supports 70+ collations for 30+ character sets. This
section indicates which character sets MySQL supports. There is
one subsection for each group of related character sets. For
each character set, the allowable collations are listed.
</p><p>
You can always list the available character sets and their
default collations with the <code class="literal">SHOW CHARACTER
SET</code> statement:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SHOW CHARACTER SET;</code></strong>
+----------+-----------------------------+---------------------+
| Charset | Description | Default collation |
+----------+-----------------------------+---------------------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci |
| dec8 | DEC West European | dec8_swedish_ci |
| cp850 | DOS West European | cp850_general_ci |
| hp8 | HP West European | hp8_english_ci |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci |
| latin1 | cp1252 West European | latin1_swedish_ci |
| latin2 | ISO 8859-2 Central European | latin2_general_ci |
| swe7 | 7bit Swedish | swe7_swedish_ci |
| ascii | US ASCII | ascii_general_ci |
| ujis | EUC-JP Japanese | ujis_japanese_ci |
| sjis | Shift-JIS Japanese | sjis_japanese_ci |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci |
| tis620 | TIS620 Thai | tis620_thai_ci |
| euckr | EUC-KR Korean | euckr_korean_ci |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci |
| greek | ISO 8859-7 Greek | greek_general_ci |
| cp1250 | Windows Central European | cp1250_general_ci |
| gbk | GBK Simplified Chinese | gbk_chinese_ci |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci |
| utf8 | UTF-8 Unicode | utf8_general_ci |
| ucs2 | UCS-2 Unicode | ucs2_general_ci |
| cp866 | DOS Russian | cp866_general_ci |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci |
| macce | Mac Central European | macce_general_ci |
| macroman | Mac West European | macroman_general_ci |
| cp852 | DOS Central European | cp852_general_ci |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci |
| cp1251 | Windows Cyrillic | cp1251_general_ci |
| cp1256 | Windows Arabic | cp1256_general_ci |
| cp1257 | Windows Baltic | cp1257_general_ci |
| binary | Binary pseudo charset | binary |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |
+----------+-----------------------------+---------------------+
</pre><p>
In cases where a character set has multiple collations, it might
not be clear which collation is most suitable for a given
application. To avoid choosing the wrong collation, it can be
helpful to perform some comparisons with representative data
values to make sure that a given collation sorts values the way
you expect.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-unicode-sets"></a>9.1.11.1. Unicode Character Sets</h4></div></div></div><p>
MySQL has two Unicode character sets. You can store text in
about 650 languages using these character sets.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">ucs2</code> (UCS-2 Unicode) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">ucs2_bin</code>
</p></li><li><p>
<code class="literal">ucs2_czech_ci</code>
</p></li><li><p>
<code class="literal">ucs2_danish_ci</code>
</p></li><li><p>
<code class="literal">ucs2_esperanto_ci</code>
</p></li><li><p>
<code class="literal">ucs2_estonian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_general_ci</code> (default)
</p></li><li><p>
<code class="literal">ucs2_hungarian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_icelandic_ci</code>
</p></li><li><p>
<code class="literal">ucs2_latvian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_lithuanian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_persian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_polish_ci</code>
</p></li><li><p>
<code class="literal">ucs2_roman_ci</code>
</p></li><li><p>
<code class="literal">ucs2_romanian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_slovak_ci</code>
</p></li><li><p>
<code class="literal">ucs2_slovenian_ci</code>
</p></li><li><p>
<code class="literal">ucs2_spanish2_ci</code>
</p></li><li><p>
<code class="literal">ucs2_spanish_ci</code>
</p></li><li><p>
<code class="literal">ucs2_swedish_ci</code>
</p></li><li><p>
<code class="literal">ucs2_turkish_ci</code>
</p></li><li><p>
<code class="literal">ucs2_unicode_ci</code>
</p></li></ul></div></li><li><p>
<code class="literal">utf8</code> (UTF-8 Unicode) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">utf8_bin</code>
</p></li><li><p>
<code class="literal">utf8_czech_ci</code>
</p></li><li><p>
<code class="literal">utf8_danish_ci</code>
</p></li><li><p>
<code class="literal">utf8_esperanto_ci</code>
</p></li><li><p>
<code class="literal">utf8_estonian_ci</code>
</p></li><li><p>
<code class="literal">utf8_general_ci</code> (default)
</p></li><li><p>
<code class="literal">utf8_hungarian_ci</code>
</p></li><li><p>
<code class="literal">utf8_icelandic_ci</code>
</p></li><li><p>
<code class="literal">utf8_latvian_ci</code>
</p></li><li><p>
<code class="literal">utf8_lithuanian_ci</code>
</p></li><li><p>
<code class="literal">utf8_persian_ci</code>
</p></li><li><p>
<code class="literal">utf8_polish_ci</code>
</p></li><li><p>
<code class="literal">utf8_roman_ci</code>
</p></li><li><p>
<code class="literal">utf8_romanian_ci</code>
</p></li><li><p>
<code class="literal">utf8_slovak_ci</code>
</p></li><li><p>
<code class="literal">utf8_slovenian_ci</code>
</p></li><li><p>
<code class="literal">utf8_spanish2_ci</code>
</p></li><li><p>
<code class="literal">utf8_spanish_ci</code>
</p></li><li><p>
<code class="literal">utf8_swedish_ci</code>
</p></li><li><p>
<code class="literal">utf8_turkish_ci</code>
</p></li><li><p>
<code class="literal">utf8_unicode_ci</code>
</p></li></ul></div></li></ul></div><p>
The MySQL implementation of UCS-2 stores characters in
big-endian byte order and does not use a byte order mark (BOM)
at the beginning of UCS-2 values. Other database systems might
use little-ending byte order or a BOM, in which case
conversion of UCS-2 values will need to be performed when
transferring data between those systems and MySQL.
</p><p>
Note that in the <code class="literal">ucs2_roman_ci</code> and
<code class="literal">utf8_roman_ci</code> collations,
<code class="literal">I</code> and <code class="literal">J</code> compare as
equals, and <code class="literal">U</code> and <code class="literal">V</code>
compare as equals.
</p><p>
The <code class="literal">ucs2_esperanto_ci</code> and
<code class="literal">utf8_esperanto_ci</code> collations were added in
MySQL 5.0.13. The <code class="literal">ucs2_hungarian_ci</code> and
<code class="literal">utf8_hungarian_ci</code> collations were added in
MySQL 5.0.19.
</p><a class="indexterm" name="id2749600"></a><p>
MySQL implements the <code class="literal">utf8_unicode_ci</code>
collation according to the Unicode Collation Algorithm (UCA)
described at
<a href="http://www.unicode.org/reports/tr10/" target="_top">http://www.unicode.org/reports/tr10/</a>. The
collation uses the version-4.0.0 UCA weight keys:
<a href="http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt" target="_top">http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt</a>.
The following discussion uses
<code class="literal">utf8_unicode_ci</code>, but it is also true for
<code class="literal">ucs2_unicode_ci</code>.
</p><p>
Currently, the <code class="literal">utf8_unicode_ci</code> collation
has only partial support for the Unicode Collation Algorithm.
Some characters are not supported yet. Also, combining marks
are not fully supported. This affects primarily Vietnamese,
Yoruba, and some smaller languages such as Navajo.
</p><p>
For any Unicode character set, operations performed using the
<code class="literal">_general_ci</code> collation are faster than those
for the <code class="literal">_unicode_ci</code> collation. For example,
comparisons for the <code class="literal">utf8_general_ci</code>
collation are faster, but slightly less correct, than
comparisons for <code class="literal">utf8_unicode_ci</code>. The reason
for this is that <code class="literal">utf8_unicode_ci</code> supports
mappings such as expansions; that is, when one character
compares as equal to combinations of other characters. For
example, in German and some other languages
“<span class="quote"><code class="literal">ß</code></span>” is equal to
“<span class="quote"><code class="literal">ss</code></span>”.
<code class="literal">utf8_unicode_ci</code> also supports contractions
and ignorable characters. <code class="literal">utf8_general_ci</code>
is a legacy collation that does not support expansions,
contractions, or ignorable characters. It can make only
one-to-one comparisons between characters.
</p><p>
To further illustrate, the following equalities hold in both
<code class="literal">utf8_general_ci</code> and
<code class="literal">utf8_unicode_ci</code> (for the effect this has in
comparisons or when doing searches, see
<a href="internationalization-localization.html#charset-collation-effect" title="9.1.5.6. Examples of the Effect of Collation">Section 9.1.5.6, “Examples of the Effect of Collation”</a>):
</p><pre class="programlisting">Ä = A
Ö = O
Ü = U
</pre><p>
A difference between the collations is that this is true for
<code class="literal">utf8_general_ci</code>:
</p><pre class="programlisting">ß = s
</pre><p>
Whereas this is true for <code class="literal">utf8_unicode_ci</code>:
</p><pre class="programlisting">ß = ss
</pre><p>
MySQL implements language-specific collations for the
<code class="literal">utf8</code> character set only if the ordering
with <code class="literal">utf8_unicode_ci</code> does not work well for
a language. For example, <code class="literal">utf8_unicode_ci</code>
works fine for German and French, so there is no need to
create special <code class="literal">utf8</code> collations for these
two languages.
</p><p>
<code class="literal">utf8_general_ci</code> also is satisfactory for
both German and French, except that
“<span class="quote"><code class="literal">ß</code></span>” is equal to
“<span class="quote"><code class="literal">s</code></span>”, and not to
“<span class="quote"><code class="literal">ss</code></span>”. If this is acceptable
for your application, then you should use
<code class="literal">utf8_general_ci</code> because it is faster.
Otherwise, use <code class="literal">utf8_unicode_ci</code> because it
is more accurate.
</p><p>
<code class="literal">utf8_swedish_ci</code>, like other
<code class="literal">utf8</code> language-specific collations, is
derived from <code class="literal">utf8_unicode_ci</code> with
additional language rules. For example, in Swedish, the
following relationship holds, which is not something expected
by a German or French speaker:
</p><pre class="programlisting">Ü = Y < Ö
</pre><p>
The <code class="literal">utf8_spanish_ci</code> and
<code class="literal">utf8_spanish2_ci</code> collations correspond to
modern Spanish and traditional Spanish, respectively. In both
collations, “<span class="quote"><code class="literal">ñ</code></span>” (n-tilde) is
a separate letter between “<span class="quote"><code class="literal">n</code></span>”
and “<span class="quote"><code class="literal">o</code></span>”. In addition, for
traditional Spanish, “<span class="quote"><code class="literal">ch</code></span>” is a
separate letter between “<span class="quote"><code class="literal">c</code></span>”
and “<span class="quote"><code class="literal">d</code></span>”, and
“<span class="quote"><code class="literal">ll</code></span>” is a separate letter
between “<span class="quote"><code class="literal">l</code></span>” and
“<span class="quote"><code class="literal">m</code></span>”
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-we-sets"></a>9.1.11.2. West European Character Sets</h4></div></div></div><p>
Western European character sets cover most West European
languages, such as French, Spanish, Catalan, Basque,
Portuguese, Italian, Albanian, Dutch, German, Danish, Swedish,
Norwegian, Finnish, Faroese, Icelandic, Irish, Scottish, and
English.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">ascii</code> (US ASCII) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">ascii_bin</code>
</p></li><li><p>
<code class="literal">ascii_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">cp850</code> (DOS West European) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp850_bin</code>
</p></li><li><p>
<code class="literal">cp850_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">dec8</code> (DEC Western European) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">dec8_bin</code>
</p></li><li><p>
<code class="literal">dec8_swedish_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">hp8</code> (HP Western European) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">hp8_bin</code>
</p></li><li><p>
<code class="literal">hp8_english_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">latin1</code> (cp1252 West European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">latin1_bin</code>
</p></li><li><p>
<code class="literal">latin1_danish_ci</code>
</p></li><li><p>
<code class="literal">latin1_general_ci</code>
</p></li><li><p>
<code class="literal">latin1_general_cs</code>
</p></li><li><p>
<code class="literal">latin1_german1_ci</code>
</p></li><li><p>
<code class="literal">latin1_german2_ci</code>
</p></li><li><p>
<code class="literal">latin1_spanish_ci</code>
</p></li><li><p>
<code class="literal">latin1_swedish_ci</code> (default)
</p></li></ul></div><p>
<code class="literal">latin1</code> is the default character set.
MySQL's <code class="literal">latin1</code> is the same as the
Windows <code class="literal">cp1252</code> character set. This
means it is the same as the official <code class="literal">ISO
8859-1</code> or IANA (Internet Assigned Numbers
Authority) <code class="literal">latin1</code>, except that IANA
<code class="literal">latin1</code> treats the code points between
<code class="literal">0x80</code> and <code class="literal">0x9f</code> as
“<span class="quote">undefined,</span>” whereas
<code class="literal">cp1252</code>, and therefore MySQL's
<code class="literal">latin1</code>, assign characters for those
positions. For example, <code class="literal">0x80</code> is the
Euro sign. For the “<span class="quote">undefined</span>” entries in
<code class="literal">cp1252</code>, MySQL translates
<code class="literal">0x81</code> to Unicode
<code class="literal">0x0081</code>, <code class="literal">0x8d</code> to
<code class="literal">0x008d</code>, <code class="literal">0x8f</code> to
<code class="literal">0x008f</code>, <code class="literal">0x90</code> to
<code class="literal">0x0090</code>, and <code class="literal">0x9d</code> to
<code class="literal">0x009d</code>.
</p><p>
The <code class="literal">latin1_swedish_ci</code> collation is the
default that probably is used by the majority of MySQL
customers. Although it is frequently said that it is based
on the Swedish/Finnish collation rules, there are Swedes
and Finns who disagree with this statement.
</p><p>
The <code class="literal">latin1_german1_ci</code> and
<code class="literal">latin1_german2_ci</code> collations are based
on the DIN-1 and DIN-2 standards, where DIN stands for
<span class="foreignphrase"><em class="foreignphrase">Deutsches Institut für
Normung</em></span> (the German equivalent of ANSI).
DIN-1 is called the “<span class="quote">dictionary collation</span>”
and DIN-2 is called the “<span class="quote">phone book
collation.</span>” For an example of the effect this has
in comparisons or when doing searches, see
<a href="internationalization-localization.html#charset-collation-effect" title="9.1.5.6. Examples of the Effect of Collation">Section 9.1.5.6, “Examples of the Effect of Collation”</a>.
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">latin1_german1_ci</code> (dictionary)
rules:
</p><pre class="programlisting">Ä = A
Ö = O
Ü = U
ß = s
</pre></li><li><p>
<code class="literal">latin1_german2_ci</code> (phone-book)
rules:
</p><pre class="programlisting">Ä = AE
Ö = OE
Ü = UE
ß = ss
</pre></li></ul></div><p>
For an example of the effect this has in comparisons or
when doing searches, see
<a href="internationalization-localization.html#charset-collation-effect" title="9.1.5.6. Examples of the Effect of Collation">Section 9.1.5.6, “Examples of the Effect of Collation”</a>.
</p><p>
In the <code class="literal">latin1_spanish_ci</code> collation,
“<span class="quote"><code class="literal">ñ</code></span>” (n-tilde) is a
separate letter between
“<span class="quote"><code class="literal">n</code></span>” and
“<span class="quote"><code class="literal">o</code></span>”.
</p></li><li><p>
<code class="literal">macroman</code> (Mac West European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">macroman_bin</code>
</p></li><li><p>
<code class="literal">macroman_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">swe7</code> (7bit Swedish) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">swe7_bin</code>
</p></li><li><p>
<code class="literal">swe7_swedish_ci</code> (default)
</p></li></ul></div></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-ce-sets"></a>9.1.11.3. Central European Character Sets</h4></div></div></div><p>
MySQL provides some support for character sets used in the
Czech Republic, Slovakia, Hungary, Romania, Slovenia, Croatia,
Poland, and Serbia (Latin).
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">cp1250</code> (Windows Central European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp1250_bin</code>
</p></li><li><p>
<code class="literal">cp1250_croatian_ci</code>
</p></li><li><p>
<code class="literal">cp1250_czech_cs</code>
</p></li><li><p>
<code class="literal">cp1250_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">cp852</code> (DOS Central European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp852_bin</code>
</p></li><li><p>
<code class="literal">cp852_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">keybcs2</code> (DOS Kamenicky Czech-Slovak)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">keybcs2_bin</code>
</p></li><li><p>
<code class="literal">keybcs2_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">latin2</code> (ISO 8859-2 Central European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">latin2_bin</code>
</p></li><li><p>
<code class="literal">latin2_croatian_ci</code>
</p></li><li><p>
<code class="literal">latin2_czech_cs</code>
</p></li><li><p>
<code class="literal">latin2_general_ci</code> (default)
</p></li><li><p>
<code class="literal">latin2_hungarian_ci</code>
</p></li></ul></div></li><li><p>
<code class="literal">macce</code> (Mac Central European)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">macce_bin</code>
</p></li><li><p>
<code class="literal">macce_general_ci</code> (default)
</p></li></ul></div></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-se-me-sets"></a>9.1.11.4. South European and Middle East Character Sets</h4></div></div></div><p>
South European and Middle Eastern character sets supported by
MySQL include Armenian, Arabic, Georgian, Greek, Hebrew, and
Turkish.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">armscii8</code> (ARMSCII-8 Armenian)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">armscii8_bin</code>
</p></li><li><p>
<code class="literal">armscii8_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">cp1256</code> (Windows Arabic) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp1256_bin</code>
</p></li><li><p>
<code class="literal">cp1256_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">geostd8</code> (GEOSTD8 Georgian) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">geostd8_bin</code>
</p></li><li><p>
<code class="literal">geostd8_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">greek</code> (ISO 8859-7 Greek) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">greek_bin</code>
</p></li><li><p>
<code class="literal">greek_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">hebrew</code> (ISO 8859-8 Hebrew) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">hebrew_bin</code>
</p></li><li><p>
<code class="literal">hebrew_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">latin5</code> (ISO 8859-9 Turkish) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">latin5_bin</code>
</p></li><li><p>
<code class="literal">latin5_turkish_ci</code> (default)
</p></li></ul></div></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-baltic-sets"></a>9.1.11.5. Baltic Character Sets</h4></div></div></div><p>
The Baltic character sets cover Estonian, Latvian, and
Lithuanian languages.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">cp1257</code> (Windows Baltic) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp1257_bin</code>
</p></li><li><p>
<code class="literal">cp1257_general_ci</code> (default)
</p></li><li><p>
<code class="literal">cp1257_lithuanian_ci</code>
</p></li></ul></div></li><li><p>
<code class="literal">latin7</code> (ISO 8859-13 Baltic) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">latin7_bin</code>
</p></li><li><p>
<code class="literal">latin7_estonian_cs</code>
</p></li><li><p>
<code class="literal">latin7_general_ci</code> (default)
</p></li><li><p>
<code class="literal">latin7_general_cs</code>
</p></li></ul></div></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-cyrillic-sets"></a>9.1.11.6. Cyrillic Character Sets</h4></div></div></div><p>
The Cyrillic character sets and collations are for use with
Belarusian, Bulgarian, Russian, Ukrainian, and Serbian
(Cyrillic) languages.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">cp1251</code> (Windows Cyrillic) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp1251_bin</code>
</p></li><li><p>
<code class="literal">cp1251_bulgarian_ci</code>
</p></li><li><p>
<code class="literal">cp1251_general_ci</code> (default)
</p></li><li><p>
<code class="literal">cp1251_general_cs</code>
</p></li><li><p>
<code class="literal">cp1251_ukrainian_ci</code>
</p></li></ul></div></li><li><p>
<code class="literal">cp866</code> (DOS Russian) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp866_bin</code>
</p></li><li><p>
<code class="literal">cp866_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">koi8r</code> (KOI8-R Relcom Russian)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">koi8r_bin</code>
</p></li><li><p>
<code class="literal">koi8r_general_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">koi8u</code> (KOI8-U Ukrainian) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">koi8u_bin</code>
</p></li><li><p>
<code class="literal">koi8u_general_ci</code> (default)
</p></li></ul></div></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="charset-asian-sets"></a>9.1.11.7. Asian Character Sets</h4></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#charset-cp932">9.1.11.7.1. The <code class="literal">cp932</code> Character Set</a></span></dt></dl></div><p>
The Asian character sets that we support include Chinese,
Japanese, Korean, and Thai. These can be complicated. For
example, the Chinese sets must allow for thousands of
different characters. See <a href="internationalization-localization.html#charset-cp932" title="9.1.11.7.1. The cp932 Character Set">Section 9.1.11.7.1, “The <code class="literal">cp932</code> Character Set”</a>, for
additional information about the <code class="literal">cp932</code> and
<code class="literal">sjis</code> character sets.
</p><p>
For answers to some common questions and problems relating
support for Asian character sets in MySQL, see
<a href="faqs.html#faqs-cjk" title="A.11. MySQL 5.0 FAQ — MySQL Chinese, Japanese, and Korean
Character Sets">Section A.11, “MySQL 5.0 FAQ — MySQL Chinese, Japanese, and Korean
Character Sets”</a>.
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">big5</code> (Big5 Traditional Chinese)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">big5_bin</code>
</p></li><li><p>
<code class="literal">big5_chinese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">cp932</code> (SJIS for Windows Japanese)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">cp932_bin</code>
</p></li><li><p>
<code class="literal">cp932_japanese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">eucjpms</code> (UJIS for Windows Japanese)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">eucjpms_bin</code>
</p></li><li><p>
<code class="literal">eucjpms_japanese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">euckr</code> (EUC-KR Korean) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">euckr_bin</code>
</p></li><li><p>
<code class="literal">euckr_korean_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">gb2312</code> (GB2312 Simplified Chinese)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">gb2312_bin</code>
</p></li><li><p>
<code class="literal">gb2312_chinese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">gbk</code> (GBK Simplified Chinese)
collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">gbk_bin</code>
</p></li><li><p>
<code class="literal">gbk_chinese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">sjis</code> (Shift-JIS Japanese) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">sjis_bin</code>
</p></li><li><p>
<code class="literal">sjis_japanese_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">tis620</code> (TIS620 Thai) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">tis620_bin</code>
</p></li><li><p>
<code class="literal">tis620_thai_ci</code> (default)
</p></li></ul></div></li><li><p>
<code class="literal">ujis</code> (EUC-JP Japanese) collations:
</p><div class="itemizedlist"><ul type="circle"><li><p>
<code class="literal">ujis_bin</code>
</p></li><li><p>
<code class="literal">ujis_japanese_ci</code> (default)
</p></li></ul></div></li></ul></div><div class="section" lang="en"><div class="titlepage"><div><div><h5 class="title"><a name="charset-cp932"></a>9.1.11.7.1. The <code class="literal">cp932</code> Character Set</h5></div></div></div><p>
<span class="bold"><strong>Why is <code class="literal">cp932</code>
needed?</strong></span>
</p><p>
In MySQL, the <code class="literal">sjis</code> character set
corresponds to the <code class="literal">Shift_JIS</code> character
set defined by IANA, which supports JIS X0201 and JIS X0208
characters. (See
<a href="http://www.iana.org/assignments/character-sets" target="_top">http://www.iana.org/assignments/character-sets</a>.)
</p><p>
However, the meaning of “<span class="quote">SHIFT JIS</span>” as a
descriptive term has become very vague and it often includes
the extensions to <code class="literal">Shift_JIS</code> that are
defined by various vendors.
</p><p>
For example, “<span class="quote">SHIFT JIS</span>” used in Japanese
Windows environments is a Microsoft extension of
<code class="literal">Shift_JIS</code> and its exact name is
<code class="literal">Microsoft Windows Codepage : 932</code> or
<code class="literal">cp932</code>. In addition to the characters
supported by <code class="literal">Shift_JIS</code>,
<code class="literal">cp932</code> supports extension characters such
as NEC special characters, NEC selected — IBM extended
characters, and IBM extended characters.
</p><p>
Many Japanese users have experienced problems using these
extension characters. These problems stem from the following
factors:
</p><div class="itemizedlist"><ul type="disc"><li><p>
MySQL automatically converts character sets.
</p></li><li><p>
Character sets are converted via Unicode
(<code class="literal">ucs2</code>).
</p></li><li><p>
The <code class="literal">sjis</code> character set does not
support the conversion of these extension characters.
</p></li><li><p>
There are several conversion rules from so-called
“<span class="quote">SHIFT JIS</span>” to Unicode, and some characters
are converted to Unicode differently depending on the
conversion rule. MySQL supports only one of these rules
(described later).
</p></li></ul></div><p>
The MySQL <code class="literal">cp932</code> character set is designed
to solve these problems. It is available as of MySQL 5.0.3.
</p><p>
Because MySQL supports character set conversion, it is
important to separate IANA <code class="literal">Shift_JIS</code> and
<code class="literal">cp932</code> into two different character sets
because they provide different conversion rules.
</p><p>
<span class="bold"><strong>How does <code class="literal">cp932</code>
differ from <code class="literal">sjis</code>?</strong></span>
</p><p>
The <code class="literal">cp932</code> character set differs from
<code class="literal">sjis</code> in the following ways:
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">cp932</code> supports NEC special
characters, NEC selected — IBM extended
characters, and IBM selected characters.
</p></li><li><p>
Some <code class="literal">cp932</code> characters have two
different code points, both of which convert to the same
Unicode code point. When converting from Unicode back to
<code class="literal">cp932</code>, one of the code points must be
selected. For this “<span class="quote">round trip conversion,</span>”
the rule recommended by Microsoft is used. (See
<a href="http://support.microsoft.com/kb/170559/EN-US/" target="_top">http://support.microsoft.com/kb/170559/EN-US/</a>.)
</p><p>
The conversion rule works like this:
</p><div class="itemizedlist"><ul type="circle"><li><p>
If the character is in both JIS X 0208 and NEC
special characters, use the code point of JIS X
0208.
</p></li><li><p>
If the character is in both NEC special characters
and IBM selected characters, use the code point of
NEC special characters.
</p></li><li><p>
If the character is in both IBM selected characters
and NEC selected — IBM extended characters,
use the code point of IBM extended characters.
</p></li></ul></div><p>
The table shown at
<a href="http://www.microsoft.com/globaldev/reference/dbcs/932.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932.htm</a>
provides information about the Unicode values of
<code class="literal">cp932</code> characters. For
<code class="literal">cp932</code> table entries with characters
under which a four-digit number appears, the number
represents the corresponding Unicode
(<code class="literal">ucs2</code>) encoding. For table entries
with an underlined two-digit value appears, there is a
range of <code class="literal">cp932</code> character values that
begin with those two digits. Clicking such a table entry
takes you to a page that displays the Unicode value for
each of the <code class="literal">cp932</code> characters that
begin with those digits.
</p><p>
The following links are of special interest. They
correspond to the encodings for the following sets of
characters:
</p><div class="itemizedlist"><ul type="circle"><li><p>
NEC special characters:
</p><pre class="programlisting"><a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_87.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_87.htm</a>
</pre></li><li><p>
NEC selected — IBM extended characters:
</p><pre class="programlisting"><a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_ED.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_ED.htm</a>
<a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_EE.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_EE.htm</a>
</pre></li><li><p>
IBM selected characters:
</p><pre class="programlisting"><a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_FA.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_FA.htm</a>
<a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_FB.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_FB.htm</a>
<a href="http://www.microsoft.com/globaldev/reference/dbcs/932/932_FC.htm" target="_top">http://www.microsoft.com/globaldev/reference/dbcs/932/932_FC.htm</a>
</pre></li></ul></div></li><li><p>
Starting from version 5.0.3, <code class="literal">cp932</code>
supports conversion of user-defined characters in
combination with <code class="literal">eucjpms</code>, and solves
the problems with
<code class="literal">sjis</code>/<code class="literal">ujis</code>
conversion. For details, please refer to
<a href="http://www.opengroup.or.jp/jvc/cde/sjis-euc-e.html" target="_top">http://www.opengroup.or.jp/jvc/cde/sjis-euc-e.html</a>.
</p></li></ul></div><p>
For some characters, conversion to and from
<code class="literal">ucs2</code> is different for
<code class="literal">sjis</code> and <code class="literal">cp932</code>. The
following tables illustrate these differences.
</p><p>
Conversion to <code class="literal">ucs2</code>:
</p><div class="informaltable"><table border="1"><colgroup><col><col><col></colgroup><tbody><tr><td><span class="bold"><strong><code class="literal">sjis</code>/<code class="literal">cp932</code>
Value</strong></span></td><td><span class="bold"><strong><code class="literal">sjis</code> ->
<code class="literal">ucs2</code> Conversion</strong></span></td><td><span class="bold"><strong><code class="literal">cp932</code> ->
<code class="literal">ucs2</code> Conversion</strong></span></td></tr><tr><td>5C</td><td>005C</td><td>005C</td></tr><tr><td>7E</td><td>007E</td><td>007E</td></tr><tr><td>815C</td><td>2015</td><td>2015</td></tr><tr><td>815F</td><td>005C</td><td>FF3C</td></tr><tr><td>8160</td><td>301C</td><td>FF5E</td></tr><tr><td>8161</td><td>2016</td><td>2225</td></tr><tr><td>817C</td><td>2212</td><td>FF0D</td></tr><tr><td>8191</td><td>00A2</td><td>FFE0</td></tr><tr><td>8192</td><td>00A3</td><td>FFE1</td></tr><tr><td>81CA</td><td>00AC</td><td>FFE2</td></tr></tbody></table></div><p>
Conversion from <code class="literal">ucs2</code>:
</p><div class="informaltable"><table border="1"><colgroup><col><col><col></colgroup><tbody><tr><td><span class="bold"><strong><code class="literal">ucs2</code> value</strong></span></td><td><span class="bold"><strong><code class="literal">ucs2</code> ->
<code class="literal">sjis</code> Conversion</strong></span></td><td><span class="bold"><strong><code class="literal">ucs2</code> ->
<code class="literal">cp932</code> Conversion</strong></span></td></tr><tr><td>005C</td><td>815F</td><td>5C</td></tr><tr><td>007E</td><td>7E</td><td>7E</td></tr><tr><td>00A2</td><td>8191</td><td>3F</td></tr><tr><td>00A3</td><td>8192</td><td>3F</td></tr><tr><td>00AC</td><td>81CA</td><td>3F</td></tr><tr><td>2015</td><td>815C</td><td>815C</td></tr><tr><td>2016</td><td>8161</td><td>3F</td></tr><tr><td>2212</td><td>817C</td><td>3F</td></tr><tr><td>2225</td><td>3F</td><td>8161</td></tr><tr><td>301C</td><td>8160</td><td>3F</td></tr><tr><td>FF0D</td><td>3F</td><td>817C</td></tr><tr><td>FF3C</td><td>3F</td><td>815F</td></tr><tr><td>FF5E</td><td>3F</td><td>8160</td></tr><tr><td>FFE0</td><td>3F</td><td>8191</td></tr><tr><td>FFE1</td><td>3F</td><td>8192</td></tr><tr><td>FFE2</td><td>3F</td><td>81CA</td></tr></tbody></table></div><p>
Users of any Japanese character sets should be aware that
using <code class="option">--character-set-client-handshake</code> (or
<code class="option">--skip-character-set-client-handshake</code>) has
an important effect. See <a href="server-administration.html#server-options" title="5.2.2. Command Options">Section 5.2.2, “Command Options”</a>.
</p></div></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="charset-configuration"></a>9.2. The Character Set Used for Data and Sorting</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="internationalization-localization.html#german-character-set">9.2.1. Using the German Character Set</a></span></dt></dl></div><a class="indexterm" name="id2753133"></a><a class="indexterm" name="id2753142"></a><a class="indexterm" name="id2753155"></a><p>
By default, MySQL uses the <code class="literal">latin1</code> (cp1252 West
European) character set and the
<code class="literal">latin1_swedish_ci</code> collation that sorts
according to Swedish/Finnish rules. These defaults are suitable
for the United States and most of Western Europe.
</p><p>
All MySQL binary distributions are compiled with
<code class="option">--with-extra-charsets=complex</code>. This adds code to
all standard programs that enables them to handle
<code class="literal">latin1</code> and all multi-byte character sets within
the binary. Other character sets are loaded from a character-set
definition file when needed.
</p><p>
The character set determines what characters are allowed in
identifiers. The collation determines how strings are sorted by
the <code class="literal">ORDER BY</code> and <code class="literal">GROUP BY</code>
clauses of the <code class="literal">SELECT</code> statement.
</p><p>
You can change the default server character set and collation with
the <code class="option">--character-set-server</code> and
<code class="option">--collation-server</code> options when you start the
server. The collation must be a legal collation for the default
character set. (Use the <code class="literal">SHOW COLLATION</code>
statement to determine which collations are available for each
character set.) See <a href="server-administration.html#server-options" title="5.2.2. Command Options">Section 5.2.2, “Command Options”</a>.
</p><p>
The character sets available depend on the
<code class="option">--with-charset=<em class="replaceable"><code>charset_name</code></em></code>
and
<code class="option">--with-extra-charsets=<em class="replaceable"><code>list-of-charsets</code></em>
| complex | all | none</code> options to
<span><strong class="command">configure</strong></span>, and the character set configuration
files listed in
<code class="filename"><em class="replaceable"><code>SHAREDIR</code></em>/charsets/Index</code>.
See <a href="installing.html#configure-options" title="2.4.15.2. Typical configure Options">Section 2.4.15.2, “Typical <span><strong class="command">configure</strong></span> Options”</a>.
</p><p>
If you change the character set when running MySQL, that may also
change the sort order. Consequently, you must run
<span><strong class="command">myisamchk -r -q
--set-collation=<em class="replaceable"><code>collation_name</code></em></strong></span>
on all <code class="literal">MyISAM</code> tables, or your indexes may not
be ordered correctly.
</p><p>
When a client connects to a MySQL server, the server indicates to
the client what the server's default character set is. The client
switches to this character set for this connection.
</p><p>
You should use
<a href="apis.html#mysql-real-escape-string" title="23.2.3.53. mysql_real_escape_string()"><code class="literal">mysql_real_escape_string()</code></a> when
escaping strings for an SQL query.
<a href="apis.html#mysql-real-escape-string" title="23.2.3.53. mysql_real_escape_string()"><code class="literal">mysql_real_escape_string()</code></a> is
identical to the old
<a href="apis.html#mysql-escape-string" title="23.2.3.16. mysql_escape_string()"><code class="literal">mysql_escape_string()</code></a> function,
except that it takes the <code class="literal">MYSQL</code> connection
handle as the first parameter so that the appropriate character
set can be taken into account when escaping characters.
</p><p>
If the client is compiled with paths that differ from where the
server is installed and the user who configured MySQL didn't
include all character sets in the MySQL binary, you must tell the
client where it can find the additional character sets it needs if
the server runs with a different character set from the client.
You can do this by specifying a
<code class="option">--character-sets-dir</code> option to indicate the path
to the directory in which the dynamic MySQL character sets are
stored. For example, you can put the following in an option file:
</p><pre class="programlisting">[client]
character-sets-dir=/usr/local/mysql/share/mysql/charsets
</pre><p>
You can force the client to use specific character set as follows:
</p><pre class="programlisting">[client]
default-character-set=<em class="replaceable"><code>charset_name</code></em>
</pre><p>
This is normally unnecessary, however.
</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="german-character-set"></a>9.2.1. Using the German Character Set</h3></div></div></div><p>
In MySQL 5.0, character set and collation are
specified separately. This means that if you want German sort
order, you should select the <code class="literal">latin1</code> character
set and either the <code class="literal">latin1_german1_ci</code> or
<code class="literal">latin1_german2_ci</code> collation. For example, to
start the server with the <code class="literal">latin1_german1_ci</code>
collation, use the
<code class="option">--character-set-server=latin1</code> and
<code class="option">--collation-server=latin1_german1_ci</code> options.
</p><p>
For information on the differences between these two collations,
see <a href="internationalization-localization.html#charset-we-sets" title="9.1.11.2. West European Character Sets">Section 9.1.11.2, “West European Character Sets”</a>.
</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="error-message-language"></a>9.3. Setting the Error Message Language</h2></div></div></div><a class="indexterm" name="id2753473"></a><a class="indexterm" name="id2753486"></a><a class="indexterm" name="id2753498"></a><a class="indexterm" name="id2753511"></a><p>
By default, <span><strong class="command">mysqld</strong></span> produces error messages in
English, but they can also be displayed in any of these other
languages: Czech, Danish, Dutch, Estonian, French, German, Greek,
Hungarian, Italian, Japanese, Korean, Norwegian, Norwegian-ny,
Polish, Portuguese, Romanian, Russian, Slovak, Spanish, or
Swedish.
</p><p>
To start <span><strong class="command">mysqld</strong></span> with a particular language for
error messages, use the <code class="option">--language</code> or
<code class="option">-L</code> option. The option value can be a language
name or the full path to the error message file. For example:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysqld --language=swedish</code></strong>
</pre><p>
Or:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysqld --language=/usr/local/share/swedish</code></strong>
</pre><p>
The language name should be specified in lowercase.
</p><p>
By default, the language files are located in the
<code class="filename">share/<em class="replaceable"><code>LANGUAGE</code></em></code>
directory under the MySQL base directory.
</p><p>
You can also change the content of the error messages produced by
the server. Details can be found in the MySQL Internals manual,
available at
<a href="http://forge.mysql.com/wiki/MySQL_Internals_Error_Messages" target="_top">http://forge.mysql.com/wiki/MySQL_Internals_Error_Messages</a>.
If you upgrade to a newer version of MySQL after changing the
error messages, remember to repeat your changes after the upgrade.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="adding-character-set"></a>9.4. Adding a New Character Set</h2></div></div></div><a class="indexterm" name="id2753627"></a><a class="indexterm" name="id2753639"></a><p>
This section discusses the procedure for adding a new character
set to MySQL. You must have a MySQL source distribution to use
these instructions. To choose the proper procedure, determine
whether the character set is simple or complex:
</p><div class="itemizedlist"><ul type="disc"><li><p>
If the character set does not need to use special string
collating routines for sorting and does not need multi-byte
character support, it is simple.
</p></li><li><p>
If it needs either of those features, it is complex.
</p></li></ul></div><p>
For example, <code class="literal">latin1</code> and
<code class="literal">danish</code> are simple character sets, whereas
<code class="literal">big5</code> and <code class="literal">czech</code> are complex
character sets.
</p><p>
In the following instructions, the name of the character set is
represented by <em class="replaceable"><code>MYSET</code></em>.
</p><p>
For a simple character set, do the following:
</p><div class="orderedlist"><ol type="1"><li><p>
Add <em class="replaceable"><code>MYSET</code></em> to the end of the
<code class="filename">sql/share/charsets/Index</code> file. Assign a
unique number to it.
</p></li><li><p>
Create the file
<code class="filename">sql/share/charsets/<em class="replaceable"><code>MYSET</code></em>.conf</code>.
(You can use a copy of
<code class="filename">sql/share/charsets/latin1.conf</code> as the
basis for this file.)
</p><p>
The syntax for the file is very simple:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Comments start with a “<span class="quote"><code class="literal">#</code></span>”
character and continue to the end of the line.
</p></li><li><p>
Words are separated by arbitrary amounts of whitespace.
</p></li><li><p>
When defining the character set, every word must be a
number in hexadecimal format.
</p></li><li><p>
The <code class="literal">ctype</code> array takes up the first 257
words. The <code class="literal">to_lower[]</code>,
<code class="literal">to_upper[]</code> and
<code class="literal">sort_order[]</code> arrays take up 256 words
each after that.
</p></li></ul></div><p>
See <a href="internationalization-localization.html#character-arrays" title="9.5. The Character Definition Arrays">Section 9.5, “The Character Definition Arrays”</a>.
</p></li><li><p>
Add the character set name to the
<code class="literal">CHARSETS_AVAILABLE</code> and
<code class="literal">COMPILED_CHARSETS</code> lists in
<code class="filename">configure.in</code>.
</p></li><li><p>
Reconfigure, recompile, and test.
</p></li></ol></div><p>
For a complex character set, do the following:
</p><div class="orderedlist"><ol type="1"><li><p>
Create the file
<code class="filename">strings/ctype-<em class="replaceable"><code>MYSET</code></em>.c</code>
in the MySQL source distribution.
</p></li><li><p>
Add <em class="replaceable"><code>MYSET</code></em> to the end of the
<code class="filename">sql/share/charsets/Index</code> file. Assign a
unique number to it.
</p></li><li><p>
Look at one of the existing <code class="filename">ctype-*.c</code>
files (such as <code class="filename">strings/ctype-big5.c</code>) to
see what needs to be defined. Note that the arrays in your
file must have names like
<code class="literal">ctype_<em class="replaceable"><code>MYSET</code></em></code>,
<code class="literal">to_lower_<em class="replaceable"><code>MYSET</code></em></code>,
and so on. These correspond to the arrays for a simple
character set. See <a href="internationalization-localization.html#character-arrays" title="9.5. The Character Definition Arrays">Section 9.5, “The Character Definition Arrays”</a>.
</p></li><li><p>
Near the top of the file, place a special comment like this:
</p><pre class="programlisting">/*
* This comment is parsed by configure to create ctype.c,
* so don't change it unless you know what you are doing.
*
* .configure. number_<em class="replaceable"><code>MYSET</code></em>=<em class="replaceable"><code>MYNUMBER</code></em>
* .configure. strxfrm_multiply_<em class="replaceable"><code>MYSET</code></em>=<em class="replaceable"><code>N</code></em>
* .configure. mbmaxlen_<em class="replaceable"><code>MYSET</code></em>=<em class="replaceable"><code>N</code></em>
*/
</pre><p>
The <span><strong class="command">configure</strong></span> program uses this comment to
include the character set into the MySQL library
automatically.
</p><p>
The <code class="literal">strxfrm_multiply</code> and
<code class="literal">mbmaxlen</code> lines are explained in the
following sections. You need include them only if you need the
string collating functions or the multi-byte character set
functions, respectively.
</p></li><li><p>
You should then create some of the following functions:
</p><div class="itemizedlist"><ul type="disc"><li><p>
<code class="literal">my_strncoll_<em class="replaceable"><code>MYSET</code></em>()</code>
</p></li><li><p>
<code class="literal">my_strcoll_<em class="replaceable"><code>MYSET</code></em>()</code>
</p></li><li><p>
<code class="literal">my_strxfrm_<em class="replaceable"><code>MYSET</code></em>()</code>
</p></li><li><p>
<code class="literal">my_like_range_<em class="replaceable"><code>MYSET</code></em>()</code>
</p></li></ul></div><p>
See <a href="internationalization-localization.html#string-collating" title="9.6. String Collating Support">Section 9.6, “String Collating Support”</a>.
</p></li><li><p>
Add the character set name to the
<code class="literal">CHARSETS_AVAILABLE</code> and
<code class="literal">COMPILED_CHARSETS</code> lists in
<code class="literal">configure.in</code>.
</p></li><li><p>
Reconfigure, recompile, and test.
</p></li></ol></div><p>
The <code class="filename">sql/share/charsets/README</code> file includes
additional instructions.
</p><p>
If you want to have the character set included in the MySQL
distribution, mail a patch to the MySQL
<code class="literal">internals</code> mailing list. See
<a href="introduction.html#mailing-lists" title="1.6.1. MySQL Mailing Lists">Section 1.6.1, “MySQL Mailing Lists”</a>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="character-arrays"></a>9.5. The Character Definition Arrays</h2></div></div></div><p>
<code class="literal">to_lower[]</code> and <code class="literal">to_upper[]</code>
are simple arrays that hold the lowercase and uppercase characters
corresponding to each member of the character set. For example:
</p><pre class="programlisting">to_lower['A'] should contain 'a'
to_upper['a'] should contain 'A'
</pre><p>
<code class="literal">sort_order[]</code> is a map indicating how characters
should be ordered for comparison and sorting purposes. Quite often
(but not for all character sets) this is the same as
<code class="literal">to_upper[]</code>, which means that sorting is
case-insensitive. MySQL sorts characters based on the values of
<code class="literal">sort_order[]</code> elements. For more complicated
sorting rules, see the discussion of string collating in
<a href="internationalization-localization.html#string-collating" title="9.6. String Collating Support">Section 9.6, “String Collating Support”</a>.
</p><p>
<code class="literal">ctype[]</code> is an array of bit values, with one
element for one character. (Note that
<code class="literal">to_lower[]</code>, <code class="literal">to_upper[]</code>, and
<code class="literal">sort_order[]</code> are indexed by character value,
but <code class="literal">ctype[]</code> is indexed by character value + 1.
This is an old legacy convention for handling
<code class="literal">EOF</code>.)
</p><p>
You can find the following bitmask definitions in
<code class="filename">m_ctype.h</code>:
</p><pre class="programlisting">#define _U 01 /* Uppercase */
#define _L 02 /* Lowercase */
#define _N 04 /* Numeral (digit) */
#define _S 010 /* Spacing character */
#define _P 020 /* Punctuation */
#define _C 040 /* Control character */
#define _B 0100 /* Blank */
#define _X 0200 /* heXadecimal digit */
</pre><p>
The <code class="literal">ctype[]</code> entry for each character should be
the union of the applicable bitmask values that describe the
character. For example, <code class="literal">'A'</code> is an uppercase
character (<code class="literal">_U</code>) as well as a hexadecimal digit
(<code class="literal">_X</code>), so <code class="literal">ctype['A'+1]</code> should
contain the value:
</p><pre class="programlisting">_U + _X = 01 + 0200 = 0201
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="string-collating"></a>9.6. String Collating Support</h2></div></div></div><a class="indexterm" name="id2754373"></a><a class="indexterm" name="id2754385"></a><p>
If the sorting rules for your language are too complex to be
handled with the simple <code class="literal">sort_order[]</code> table, you
need to use the string collating functions.
</p><p>
The best documentation for this is the existing character sets.
Look at the <code class="literal">big5</code>, <code class="literal">czech</code>,
<code class="literal">gbk</code>, <code class="literal">sjis</code>, and
<code class="literal">tis160</code> character sets for examples.
</p><p>
You must specify the
<code class="literal">strxfrm_multiply_<em class="replaceable"><code>MYSET</code></em>=<em class="replaceable"><code>N</code></em></code>
value in the special comment at the top of the file.
<em class="replaceable"><code>N</code></em> should be set to the maximum ratio
the strings may grow during
<code class="literal">my_strxfrm_<em class="replaceable"><code>MYSET</code></em></code> (it
must be a positive integer).
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="multi-byte-characters"></a>9.7. Multi-Byte Character Support</h2></div></div></div><a class="indexterm" name="id2754481"></a><a class="indexterm" name="id2754493"></a><p>
If you want to add support for a new character set that includes
multi-byte characters, you need to use the multi-byte character
functions.
</p><p>
The best documentation for this is the existing character sets.
Look at the <code class="literal">euc_kr</code>, <code class="literal">gb2312</code>,
<code class="literal">gbk</code>, <code class="literal">sjis</code>, and
<code class="literal">ujis</code> character sets for examples. These are
implemented in the
<code class="filename">ctype-<em class="replaceable"><code>charset_name</code></em>.c</code>
files in the <code class="filename">strings</code> directory.
</p><p>
You must specify the
<code class="literal">mbmaxlen_<em class="replaceable"><code>MYSET</code></em>=<em class="replaceable"><code>N</code></em></code>
value in the special comment at the top of the source file.
<em class="replaceable"><code>N</code></em> should be set to the size in bytes of
the largest character in the set.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="problems-with-character-sets"></a>9.8. Problems With Character Sets</h2></div></div></div><p>
If you try to use a character set that is not compiled into your
binary, you might run into the following problems:
</p><div class="itemizedlist"><ul type="disc"><li><p>
Your program uses an incorrect path to determine where the
character sets are stored. (Default
<code class="filename">/usr/local/mysql/share/mysql/charsets</code>).
This can be fixed by using the
<code class="option">--character-sets-dir</code> option when you run the
program in question.
</p></li><li><p>
The character set is a multi-byte character set that cannot be
loaded dynamically. In this case, you must recompile the
program with support for the character set.
</p></li><li><p>
The character set is a dynamic character set, but you do not
have a configure file for it. In this case, you should install
the configure file for the character set from a new MySQL
distribution.
</p></li><li><p>
If your <code class="filename">Index</code> file does not contain the
name for the character set, your program displays the
following error message:
</p><pre class="programlisting">ERROR 1105: File '/usr/local/share/mysql/charsets/?.conf'
not found (Errcode: 2)
</pre><p>
In this case, you should either get a new
<code class="literal">Index</code> file or manually add the name of any
missing character sets to the current file.
</p></li></ul></div><p>
For <code class="literal">MyISAM</code> tables, you can check the character
set name and number for a table with <span><strong class="command">myisamchk -dvv
<em class="replaceable"><code>tbl_name</code></em></strong></span>.
</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="time-zone-support"></a>9.9. MySQL Server Time Zone Support</h2></div></div></div><p>
The MySQL server maintains several time zone settings:
</p><div class="itemizedlist"><ul type="disc"><li><p>
The system time zone. When the server starts, it attempts to
determine the time zone of the host machine and uses it to set
the <code class="literal">system_time_zone</code> system variable. The
value does not change thereafter.
</p><p>
You can set the system time zone for MySQL Server at startup
with the
<code class="option">--timezone=<em class="replaceable"><code>timezone_name</code></em></code>
option to <span><strong class="command">mysqld_safe</strong></span>. You can also set it
by setting the <code class="literal">TZ</code> environment variable
before you start <span><strong class="command">mysqld</strong></span>. The allowable
values for <code class="option">--timezone</code> or
<code class="literal">TZ</code> are system-dependent. Consult your
operating system documentation to see what values are
acceptable.
</p></li><li><p>
The server's current time zone. The global
<code class="literal">time_zone</code> system variable indicates the
time zone the server currently is operating in. The initial
value for <code class="literal">time_zone</code> is
<code class="literal">'SYSTEM'</code>, which indicates that the server
time zone is the same as the system time zone.
</p><p>
The initial global server time zone value can be specified
explicitly at startup with the
<code class="option">--default-time-zone=<em class="replaceable"><code>timezone</code></em></code>
option on the command line, or you can use the following line
in an option file:
</p><pre class="programlisting">default-time-zone='<em class="replaceable"><code>timezone</code></em>'
</pre><p>
If you have the <code class="literal">SUPER</code> privilege, you can
set the global server time zone value at runtime with this
statement:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SET GLOBAL time_zone = <em class="replaceable"><code>timezone</code></em>;</code></strong>
</pre></li><li><p>
Per-connection time zones. Each client that connects has its
own time zone setting, given by the session
<code class="literal">time_zone</code> variable. Initially, the session
variable takes its value from the global
<code class="literal">time_zone</code> variable, but the client can
change its own time zone with this statement:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SET time_zone = <em class="replaceable"><code>timezone</code></em>;</code></strong>
</pre></li></ul></div><p>
The current session time zone setting affects display and storage
of time values that are zone-sensitive. This includes the values
displayed by functions such as
<a href="functions.html#function_now"><code class="literal">NOW()</code></a> or
<a href="functions.html#function_curtime"><code class="literal">CURTIME()</code></a>, and values stored in
and retrieved from <code class="literal">TIMESTAMP</code> columns. Values
for <code class="literal">TIMESTAMP</code> columns are converted from the
current time zone to UTC for storage, and from UTC to the current
time zone for retrieval. The current time zone setting does not
affect values displayed by functions such as
<a href="functions.html#function_utc-timestamp"><code class="literal">UTC_TIMESTAMP()</code></a> or values in
<code class="literal">DATE</code>, <code class="literal">TIME</code>, or
<code class="literal">DATETIME</code> columns.
</p><p>
The current values of the global and client-specific time zones
can be retrieved like this:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT @@global.time_zone, @@session.time_zone;</code></strong>
</pre><p>
<em class="replaceable"><code>timezone</code></em> values can be given in several
formats, none of which are case sensitive:
</p><div class="itemizedlist"><ul type="disc"><li><p>
The value <code class="literal">'SYSTEM'</code> indicates that the time
zone should be the same as the system time zone.
</p></li><li><p>
The value can be given as a string indicating an offset from
UTC, such as <code class="literal">'+10:00'</code> or
<code class="literal">'-6:00'</code>.
</p></li><li><p>
The value can be given as a named time zone, such as
<code class="literal">'Europe/Helsinki'</code>,
<code class="literal">'US/Eastern'</code>, or <code class="literal">'MET'</code>.
Named time zones can be used only if the time zone information
tables in the <code class="literal">mysql</code> database have been
created and populated.
</p></li></ul></div><p>
The MySQL installation procedure creates the time zone tables in
the <code class="literal">mysql</code> database, but does not load them. You
must do so manually using the following instructions. (If you are
upgrading to MySQL 4.1.3 or later from an earlier version, you can
create the tables by upgrading your <code class="literal">mysql</code>
database. Use the instructions in <a href="server-administration.html#mysql-upgrade" title="5.5.8. mysql_upgrade — Check Tables for MySQL Upgrade">Section 5.5.8, “<span><strong class="command">mysql_upgrade</strong></span> — Check Tables for MySQL Upgrade”</a>.
After creating the tables, you can load them.)
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Loading the time zone information is not necessarily a one-time
operation because the information changes occasionally. For
example, the rules for Daylight Saving Time in the United
States, Mexico, and parts of Canada changed in 2007. When such
changes occur, applications that use the old rules become out of
date and you may find it necessary to reload the time zone
tables to keep the information used by your MySQL server
current. See the notes at the end of this section.
</p></div><p>
If your system has its own <em class="firstterm">zoneinfo</em>
database (the set of files describing time zones), you should use
the <span><strong class="command">mysql_tzinfo_to_sql</strong></span> program for filling the
time zone tables. Examples of such systems are Linux, FreeBSD, Sun
Solaris, and Mac OS X. One likely location for these files is the
<code class="filename">/usr/share/zoneinfo</code> directory. If your system
does not have a zoneinfo database, you can use the downloadable
package described later in this section.
</p><p>
The <span><strong class="command">mysql_tzinfo_to_sql</strong></span> program is used to load
the time zone tables. On the command line, pass the zoneinfo
directory pathname to <span><strong class="command">mysql_tzinfo_to_sql</strong></span> and
send the output into the <span><strong class="command">mysql</strong></span> program. For
example:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql</code></strong>
</pre><p>
<span><strong class="command">mysql_tzinfo_to_sql</strong></span> reads your system's time
zone files and generates SQL statements from them.
<span><strong class="command">mysql</strong></span> processes those statements to load the
time zone tables.
</p><p>
<span><strong class="command">mysql_tzinfo_to_sql</strong></span> also can be used to load a
single time zone file or to generate leap second information:
</p><div class="itemizedlist"><ul type="disc"><li><p>
To load a single time zone file
<em class="replaceable"><code>tz_file</code></em> that corresponds to a time
zone name <em class="replaceable"><code>tz_name</code></em>, invoke
<span><strong class="command">mysql_tzinfo_to_sql</strong></span> like this:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysql_tzinfo_to_sql <em class="replaceable"><code>tz_file</code></em> <em class="replaceable"><code>tz_name</code></em> | mysql -u root mysql</code></strong>
</pre><p>
With this approach, you must execute a separate command to
load the time zone file for each named zone that the server
needs to know about.
</p></li><li><p>
If your time zone needs to account for leap seconds,
initialize the leap second information like this, where
<em class="replaceable"><code>tz_file</code></em> is the name of your time
zone file:
</p><pre class="programlisting">shell> <strong class="userinput"><code>mysql_tzinfo_to_sql --leap <em class="replaceable"><code>tz_file</code></em> | mysql -u root mysql</code></strong>
</pre></li><li><p>
After running <span><strong class="command">mysql_tzinfo_to_sql</strong></span>, it is
best to restart the server so that it does not continue to use
any previously cached time zone data.
</p></li></ul></div><p>
If your system is one that has no zoneinfo database (for example,
Windows or HP-UX), you can use the package of pre-built time zone
tables that is available for download at the MySQL Developer Zone:
</p><pre class="programlisting"><a href="http://dev.mysql.com/downloads/timezones.html" target="_top">http://dev.mysql.com/downloads/timezones.html</a>
</pre><p>
This time zone package contains <code class="filename">.frm</code>,
<code class="filename">.MYD</code>, and <code class="filename">.MYI</code> files for
the <code class="literal">MyISAM</code> time zone tables. These tables
should be part of the <code class="literal">mysql</code> database, so you
should place the files in the <code class="filename">mysql</code>
subdirectory of your MySQL server's data directory. The server
should be stopped while you do this and restarted afterward.
</p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>
Do not use the downloadable package if your system has a
zoneinfo database. Use the
<span><strong class="command">mysql_tzinfo_to_sql</strong></span> utility instead.
Otherwise, you may cause a difference in datetime handling
between MySQL and other applications on your system.
</p></div><p>
For information about time zone settings in replication setup,
please see <a href="replication.html#replication-features" title="15.3.1. Replication Features and Issues">Section 15.3.1, “Replication Features and Issues”</a>.
</p><p>
<span class="bold"><strong>Staying Current with Time Zone
Changes</strong></span>
</p><p>
As mentioned earlier, when the time zone rules change,
applications that use the old rules become out of date. To stay
current, it is necessary to make sure that your system uses
current time zone information is used. For MySQL, there are two
factors to consider in staying current:
</p><div class="itemizedlist"><ul type="disc"><li><p>
The operating system time affects the value that the MySQL
server uses for times if its time zone is set to
<code class="literal">SYSTEM</code>. Make sure that your operating
system is using the latest time zone information. For most
operating systems, the latest update or service pack prepares
your system for the time changes. Check the Web site for your
operating system vendor for an update that addresses the time
changes.
</p></li><li><p>
If you replace the system's
<code class="filename">/etc/localtime</code> timezone file with a
verion that uses rules differing from those in effect at
<span><strong class="command">mysqld</strong></span> startup, you should restart
<span><strong class="command">mysqld</strong></span> so that it uses the updated rules.
Otherwise, <span><strong class="command">mysqld</strong></span> might not notice when the
system changes its time.
</p></li><li><p>
If you use named time zones with MySQL, make sure that the
time zone tables in the <code class="literal">mysql</code> database are
up to date. If your system has its own zoneinfo database, you
should reload the MySQL time zone tables whenever the zoneinfo
database is updated, using the instructions given earlier in
this section. For systems that do not have their own zoneinfo
database, check the MySQL Developer Zone for updates. When a
new update is available, download it and use it to replace
your current time zone tables. <span><strong class="command">mysqld</strong></span>
caches time zone information that it looks up, so after
replacing the time zone tables, you should restart
<span><strong class="command">mysqld</strong></span> to make sure that it does not
continue to serve outdated time zone data.
</p></li></ul></div><p>
If you are uncertain whether named time zones are available, for
use either as the server's time zone setting or by clients that
set their own time zone, check whether your time zone tables are
empty. The following query determines whether the table that
contains time zone names has any rows:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT COUNT(*) FROM mysql.time_zone_name;</code></strong>
+----------+
| COUNT(*) |
+----------+
| 0 |
+----------+
</pre><p>
A count of zero indicates that the table is empty. In this case,
no one can be using named time zones, and you don't need to update
the tables. A count greater than zero indicates that the table is
not empty and that its contents are available to be used for named
time zone support. In this case, you should be sure to reload your
time zone tables so that anyone who uses named time zones will get
correct query results.
</p><p>
To check whether your MySQL installation is updated properly for a
change in Daylight Saving Time rules, use a test like the one
following. The example uses values that are appropriate for the
2007 DST 1-hour change that occurs in the United States on March
11 at 2 a.m.
</p><p>
The test uses these two queries:
</p><pre class="programlisting">SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');
SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');
</pre><p>
The two time values indicate the times at which the DST change
occurs, and the use of named time zones requires that the time
zone tables be used. The desired result is that both queries
return the same result (the input time, converted to the
equivalent value in the 'US/Central' time zone).
</p><p>
Before updating the time zone tables, you would see an incorrect
result like this:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');</code></strong>
+------------------------------------------------------------+
| CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central') |
+------------------------------------------------------------+
| 2007-03-11 01:00:00 |
+------------------------------------------------------------+
mysql> <strong class="userinput"><code>SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');</code></strong>
+------------------------------------------------------------+
| CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central') |
+------------------------------------------------------------+
| 2007-03-11 02:00:00 |
+------------------------------------------------------------+
</pre><p>
After updating the tables, you should see the correct result:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');</code></strong>
+------------------------------------------------------------+
| CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central') |
+------------------------------------------------------------+
| 2007-03-11 01:00:00 |
+------------------------------------------------------------+
mysql> <strong class="userinput"><code>SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');</code></strong>
+------------------------------------------------------------+
| CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central') |
+------------------------------------------------------------+
| 2007-03-11 01:00:00 |
+------------------------------------------------------------+
</pre></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="locale-support"></a>9.10. MySQL Server Locale Support</h2></div></div></div><p>
Beginning with MySQL 5.0.25, the locale indicated by the
<code class="literal">lc_time_names</code> system variable controls the
language used to display day and month names and abbreviations.
This variable affects the output from the
<a href="functions.html#function_date-format"><code class="literal">DATE_FORMAT()</code></a>,
<a href="functions.html#function_dayname"><code class="literal">DAYNAME()</code></a> and
<a href="functions.html#function_monthname"><code class="literal">MONTHNAME()</code></a> functions.
</p><p>
Locale names are POSIX-style values such as
<code class="literal">'ja_JP'</code> or <code class="literal">'pt_BR'</code>. The
default value is <code class="literal">'en_US'</code> regardless of your
system's locale setting, but any client can examine or set its
<code class="literal">lc_time_names</code> value as shown in the following
example:
</p><pre class="programlisting">mysql> <strong class="userinput"><code>SET NAMES 'utf8';</code></strong>
Query OK, 0 rows affected (0.09 sec)
mysql> <strong class="userinput"><code>SELECT @@lc_time_names;</code></strong>
+-----------------+
| @@lc_time_names |
+-----------------+
| en_US |
+-----------------+
1 row in set (0.00 sec)
mysql> <strong class="userinput"><code>SELECT DAYNAME('2010-01-01'), MONTHNAME('2010-01-01');</code></strong>
+-----------------------+-------------------------+
| DAYNAME('2010-01-01') | MONTHNAME('2010-01-01') |
+-----------------------+-------------------------+
| Friday | January |
+-----------------------+-------------------------+
1 row in set (0.00 sec)
mysql> <strong class="userinput"><code>SELECT DATE_FORMAT('2010-01-01','%W %a %M %b');</code></strong>
+-----------------------------------------+
| DATE_FORMAT('2010-01-01','%W %a %M %b') |
+-----------------------------------------+
| Friday Fri January Jan |
+-----------------------------------------+
1 row in set (0.00 sec)
mysql> <strong class="userinput"><code>SET lc_time_names = 'es_MX';</code></strong>
Query OK, 0 rows affected (0.00 sec)
mysql> <strong class="userinput"><code>SELECT @@lc_time_names;</code></strong>
+-----------------+
| @@lc_time_names |
+-----------------+
| es_MX |
+-----------------+
1 row in set (0.00 sec)
mysql> <strong class="userinput"><code>SELECT DAYNAME('2010-01-01'), MONTHNAME('2010-01-01');</code></strong>
+-----------------------+-------------------------+
| DAYNAME('2010-01-01') | MONTHNAME('2010-01-01') |
+-----------------------+-------------------------+
| viernes | enero |
+-----------------------+-------------------------+
1 row in set (0.00 sec)
mysql> <strong class="userinput"><code>SELECT DATE_FORMAT('2010-01-01','%W %a %M %b');</code></strong>
+-----------------------------------------+
| DATE_FORMAT('2010-01-01','%W %a %M %b') |
+-----------------------------------------+
| viernes vie enero ene |
+-----------------------------------------+
1 row in set (0.00 sec)
</pre><p>
The day or month name for each of the affected functions is
converted from <code class="literal">utf8</code> to the character set
indicated by the <code class="literal">character_set_connection</code>
system variable.
</p><p>
<code class="literal">lc_time_names</code> may be set to any of the
following locale values:
</p><div class="informaltable"><table border="1"><colgroup><col><col></colgroup><tbody><tr><td><code class="literal">ar_AE</code>: Arabic - United Arab Emirates</td><td><code class="literal">ar_BH</code>: Arabic - Bahrain</td></tr><tr><td><code class="literal">ar_DZ</code>: Arabic - Algeria</td><td><code class="literal">ar_EG</code>: Arabic - Egypt</td></tr><tr><td><code class="literal">ar_IN</code>: Arabic - Iran</td><td><code class="literal">ar_IQ</code>: Arabic - Iraq</td></tr><tr><td><code class="literal">ar_JO</code>: Arabic - Jordan</td><td><code class="literal">ar_KW</code>: Arabic - Kuwait</td></tr><tr><td><code class="literal">ar_LB</code>: Arabic - Lebanon</td><td><code class="literal">ar_LY</code>: Arabic - Libya</td></tr><tr><td><code class="literal">ar_MA</code>: Arabic - Morocco</td><td><code class="literal">ar_OM</code>: Arabic - Oman</td></tr><tr><td><code class="literal">ar_QA</code>: Arabic - Qatar</td><td><code class="literal">ar_SA</code>: Arabic - Saudi Arabia</td></tr><tr><td><code class="literal">ar_SD</code>: Arabic - Sudan</td><td><code class="literal">ar_SY</code>: Arabic - Syria</td></tr><tr><td><code class="literal">ar_TN</code>: Arabic - Tunisia</td><td><code class="literal">ar_YE</code>: Arabic - Yemen</td></tr><tr><td><code class="literal">be_BY</code>: Belarusian - Belarus</td><td><code class="literal">bg_BG</code>: Bulgarian - Bulgaria</td></tr><tr><td><code class="literal">ca_ES</code>: Catalan - Catalan</td><td><code class="literal">cs_CZ</code>: Czech - Czech Republic</td></tr><tr><td><code class="literal">da_DK</code>: Danish - Denmark</td><td><code class="literal">de_AT</code>: German - Austria</td></tr><tr><td><code class="literal">de_BE</code>: German - Belgium</td><td><code class="literal">de_CH</code>: German - Switzerland</td></tr><tr><td><code class="literal">de_DE</code>: German - Germany</td><td><code class="literal">de_LU</code>: German - Luxembourg</td></tr><tr><td><code class="literal">EE</code>: Estonian - Estonia</td><td><code class="literal">en_AU</code>: English - Australia</td></tr><tr><td><code class="literal">en_CA</code>: English - Canada</td><td><code class="literal">en_GB</code>: English - United Kingdom</td></tr><tr><td><code class="literal">en_IN</code>: English - India</td><td><code class="literal">en_NZ</code>: English - New Zealand</td></tr><tr><td><code class="literal">en_PH</code>: English - Philippines</td><td><code class="literal">en_US</code>: English - United States</td></tr><tr><td><code class="literal">en_ZA</code>: English - South Africa</td><td><code class="literal">en_ZW</code>: English - Zimbabwe</td></tr><tr><td><code class="literal">es_AR</code>: Spanish - Argentina</td><td><code class="literal">es_BO</code>: Spanish - Bolivia</td></tr><tr><td><code class="literal">es_CL</code>: Spanish - Chile</td><td><code class="literal">es_CO</code>: Spanish - Columbia</td></tr><tr><td><code class="literal">es_CR</code>: Spanish - Costa Rica</td><td><code class="literal">es_DO</code>: Spanish - Dominican Republic</td></tr><tr><td><code class="literal">es_EC</code>: Spanish - Ecuador</td><td><code class="literal">es_ES</code>: Spanish - Spain</td></tr><tr><td><code class="literal">es_GT</code>: Spanish - Guatemala</td><td><code class="literal">es_HN</code>: Spanish - Honduras</td></tr><tr><td><code class="literal">es_MX</code>: Spanish - Mexico</td><td><code class="literal">es_NI</code>: Spanish - Nicaragua</td></tr><tr><td><code class="literal">es_PA</code>: Spanish - Panama</td><td><code class="literal">es_PE</code>: Spanish - Peru</td></tr><tr><td><code class="literal">es_PR</code>: Spanish - Puerto Rico</td><td><code class="literal">es_PY</code>: Spanish - Paraguay</td></tr><tr><td><code class="literal">es_SV</code>: Spanish - El Salvador</td><td><code class="literal">es_US</code>: Spanish - United States</td></tr><tr><td><code class="literal">es_UY</code>: Spanish - Uruguay</td><td><code class="literal">es_VE</code>: Spanish - Venezuela</td></tr><tr><td><code class="literal">eu_ES</code>: Basque - Basque</td><td><code class="literal">fi_FI</code>: Finnish - Finland</td></tr><tr><td><code class="literal">fo_FO</code>: Faroese - Faroe Islands</td><td><code class="literal">fr_BE</code>: French - Belgium</td></tr><tr><td><code class="literal">fr_CA</code>: French - Canada</td><td><code class="literal">fr_CH</code>: French - Switzerland</td></tr><tr><td><code class="literal">fr_FR</code>: French - France</td><td><code class="literal">fr_LU</code>: French - Luxembourg</td></tr><tr><td><code class="literal">gl_ES</code>: Galician - Galician</td><td><code class="literal">gu_IN</code>: Gujarati - India</td></tr><tr><td><code class="literal">he_IL</code>: Hebrew - Israel</td><td><code class="literal">hi_IN</code>: Hindi - India</td></tr><tr><td><code class="literal">hr_HR</code>: Croatian - Croatia</td><td><code class="literal">hu_HU</code>: Hungarian - Hungary</td></tr><tr><td><code class="literal">id_ID</code>: Indonesian - Indonesia</td><td><code class="literal">is_IS</code>: Icelandic - Iceland</td></tr><tr><td><code class="literal">it_CH</code>: Italian - Switzerland</td><td><code class="literal">it_IT</code>: Italian - Italy</td></tr><tr><td><code class="literal">ja_JP</code>: Japanese - Japan</td><td><code class="literal">ko_KR</code>: Korean - Korea</td></tr><tr><td><code class="literal">lt_LT</code>: Lithuanian - Lithuania</td><td><code class="literal">lv_LV</code>: Latvian - Latvia</td></tr><tr><td><code class="literal">mk_MK</code>: Macedonian - FYROM</td><td><code class="literal">mn_MN</code>: Mongolia - Mongolian</td></tr><tr><td><code class="literal">ms_MY</code>: Malay - Malaysia</td><td><code class="literal">nb_NO</code>: Norwegian(Bokml) - Norway</td></tr><tr><td><code class="literal">nl_BE</code>: Dutch - Belgium</td><td><code class="literal">nl_NL</code>: Dutch - The Netherlands</td></tr><tr><td><code class="literal">no_NO</code>: Norwegian - Norway</td><td><code class="literal">pl_PL</code>: Polish - Poland</td></tr><tr><td><code class="literal">pt_BR</code>: Portugese - Brazil</td><td><code class="literal">pt_PT</code>: Portugese - Portugal</td></tr><tr><td><code class="literal">ro_RO</code>: Romanian - Romania</td><td><code class="literal">ru_RU</code>: Russian - Russia</td></tr><tr><td><code class="literal">ru_UA</code>: Russian - Ukraine</td><td><code class="literal">sk_SK</code>: Slovak - Slovakia</td></tr><tr><td><code class="literal">sl_SI</code>: Slovenian - Slovenia</td><td><code class="literal">sq_AL</code>: Albanian - Albania</td></tr><tr><td><code class="literal">sr_YU</code>: Serbian - Yugoslavia</td><td><code class="literal">sv_FI</code>: Swedish - Finland</td></tr><tr><td><code class="literal">sv_SE</code>: Swedish - Sweden</td><td><code class="literal">ta_IN</code>: Tamil - India</td></tr><tr><td><code class="literal">te_IN</code>: Telugu - India</td><td><code class="literal">th_TH</code>: Thai - Thailand</td></tr><tr><td><code class="literal">tr_TR</code>: Turkish - Turkey</td><td><code class="literal">uk_UA</code>: Ukrainian - Ukraine</td></tr><tr><td><code class="literal">ur_PK</code>: Urdu - Pakistan</td><td><code class="literal">vi_VN</code>: Vietnamese - Vietnam</td></tr><tr><td><code class="literal">zh_CN</code>: Chinese - Peoples Republic of China</td><td><code class="literal">zh_HK</code>: Chinese - Hong Kong SAR</td></tr><tr><td><code class="literal">zh_TW</code>: Chinese - Taiwan</td><td> </td></tr></tbody></table></div><p>
<code class="literal">lc_time_names</code> currently does not affect the
<a href="functions.html#function_str-to-date"><code class="literal">STR_TO_DATE()</code></a> or
<a href="functions.html#function_get-format"><code class="literal">GET_FORMAT()</code></a> function.
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="language-structure.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="data-types.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 8. Language Structure </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 10. Data Types</td></tr></table></div></body></html>
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