<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>CREATE TABLE</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION" /><link rel="next" href="sql-createtableas.html" title="CREATE TABLE AS" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE TABLE</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-createtableas.html" title="CREATE TABLE AS">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATETABLE"><div class="titlepage"></div><a id="id-1.9.3.85.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE TABLE</span></h2><p>CREATE TABLE — define a new table</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em> ( [
{ <em class="replaceable"><code>column_name</code></em> <em class="replaceable"><code>data_type</code></em> [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
| <em class="replaceable"><code>table_constraint</code></em>
| LIKE <em class="replaceable"><code>source_table</code></em> [ <em class="replaceable"><code>like_option</code></em> ... ] }
[, ... ]
] )
[ INHERITS ( <em class="replaceable"><code>parent_table</code></em> [, ... ] ) ]
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em>
OF <em class="replaceable"><code>type_name</code></em> [ (
{ <em class="replaceable"><code>column_name</code></em> [ WITH OPTIONS ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
| <em class="replaceable"><code>table_constraint</code></em> }
[, ... ]
) ]
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <em class="replaceable"><code>table_name</code></em>
PARTITION OF <em class="replaceable"><code>parent_table</code></em> [ (
{ <em class="replaceable"><code>column_name</code></em> [ WITH OPTIONS ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]
| <em class="replaceable"><code>table_constraint</code></em> }
[, ... ]
) ] { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }
[ PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> ] [, ... ] ) ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]
<span class="phrase">where <em class="replaceable"><code>column_constraint</code></em> is:</span>
[ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]
{ NOT NULL |
NULL |
CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |
DEFAULT <em class="replaceable"><code>default_expr</code></em> |
GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ] |
UNIQUE <em class="replaceable"><code>index_parameters</code></em> |
PRIMARY KEY <em class="replaceable"><code>index_parameters</code></em> |
REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
[ ON DELETE <em class="replaceable"><code>action</code></em> ] [ ON UPDATE <em class="replaceable"><code>action</code></em> ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
<span class="phrase">and <em class="replaceable"><code>table_constraint</code></em> is:</span>
[ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]
{ CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |
UNIQUE ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |
PRIMARY KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |
EXCLUDE [ USING <em class="replaceable"><code>index_method</code></em> ] ( <em class="replaceable"><code>exclude_element</code></em> WITH <em class="replaceable"><code>operator</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> [ WHERE ( <em class="replaceable"><code>predicate</code></em> ) ] |
FOREIGN KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> [, ... ] ) ]
[ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <em class="replaceable"><code>action</code></em> ] [ ON UPDATE <em class="replaceable"><code>action</code></em> ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
<span class="phrase">and <em class="replaceable"><code>like_option</code></em> is:</span>
{ INCLUDING | EXCLUDING } { COMMENTS | CONSTRAINTS | DEFAULTS | IDENTITY | INDEXES | STATISTICS | STORAGE | ALL }
<span class="phrase">and <em class="replaceable"><code>partition_bound_spec</code></em> is:</span>
IN ( { <em class="replaceable"><code>numeric_literal</code></em> | <em class="replaceable"><code>string_literal</code></em> | TRUE | FALSE | NULL } [, ...] ) |
FROM ( { <em class="replaceable"><code>numeric_literal</code></em> | <em class="replaceable"><code>string_literal</code></em> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] )
TO ( { <em class="replaceable"><code>numeric_literal</code></em> | <em class="replaceable"><code>string_literal</code></em> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] ) |
WITH ( MODULUS <em class="replaceable"><code>numeric_literal</code></em>, REMAINDER <em class="replaceable"><code>numeric_literal</code></em> )
<span class="phrase"><em class="replaceable"><code>index_parameters</code></em> in <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>, and <code class="literal">EXCLUDE</code> constraints are:</span>
[ INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]
[ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) ]
[ USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]
<span class="phrase"><em class="replaceable"><code>exclude_element</code></em> in an <code class="literal">EXCLUDE</code> constraint is:</span>
{ <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ <em class="replaceable"><code>opclass</code></em> ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]
</pre></div><div class="refsect1" id="SQL-CREATETABLE-DESCRIPTION"><h2>Description</h2><p>
<code class="command">CREATE TABLE</code> will create a new, initially empty table
in the current database. The table will be owned by the user issuing the
command.
</p><p>
If a schema name is given (for example, <code class="literal">CREATE TABLE
myschema.mytable ...</code>) then the table is created in the specified
schema. Otherwise it is created in the current schema. Temporary
tables exist in a special schema, so a schema name cannot be given
when creating a temporary table. The name of the table must be
distinct from the name of any other table, sequence, index, view,
or foreign table in the same schema.
</p><p>
<code class="command">CREATE TABLE</code> also automatically creates a data
type that represents the composite type corresponding
to one row of the table. Therefore, tables cannot have the same
name as any existing data type in the same schema.
</p><p>
The optional constraint clauses specify constraints (tests) that
new or updated rows must satisfy for an insert or update operation
to succeed. A constraint is an SQL object that helps define the
set of valid values in the table in various ways.
</p><p>
There are two ways to define constraints: table constraints and
column constraints. A column constraint is defined as part of a
column definition. A table constraint definition is not tied to a
particular column, and it can encompass more than one column.
Every column constraint can also be written as a table constraint;
a column constraint is only a notational convenience for use when the
constraint only affects one column.
</p><p>
To be able to create a table, you must have <code class="literal">USAGE</code>
privilege on all column types or the type in the <code class="literal">OF</code>
clause, respectively.
</p></div><div class="refsect1" id="id-1.9.3.85.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt id="SQL-CREATETABLE-TEMPORARY"><span class="term"><code class="literal">TEMPORARY</code> or <code class="literal">TEMP</code></span></dt><dd><p>
If specified, the table is created as a temporary table.
Temporary tables are automatically dropped at the end of a
session, or optionally at the end of the current transaction
(see <code class="literal">ON COMMIT</code> below). Existing permanent
tables with the same name are not visible to the current session
while the temporary table exists, unless they are referenced
with schema-qualified names. Any indexes created on a temporary
table are automatically temporary as well.
</p><p>
The <a class="link" href="routine-vacuuming.html#AUTOVACUUM" title="24.1.6. The Autovacuum Daemon">autovacuum daemon</a> cannot
access and therefore cannot vacuum or analyze temporary tables.
For this reason, appropriate vacuum and analyze operations should be
performed via session SQL commands. For example, if a temporary
table is going to be used in complex queries, it is wise to run
<code class="command">ANALYZE</code> on the temporary table after it is populated.
</p><p>
Optionally, <code class="literal">GLOBAL</code> or <code class="literal">LOCAL</code>
can be written before <code class="literal">TEMPORARY</code> or <code class="literal">TEMP</code>.
This presently makes no difference in <span class="productname">PostgreSQL</span>
and is deprecated; see
<a class="xref" href="sql-createtable.html#SQL-CREATETABLE-COMPATIBILITY" title="Compatibility">Compatibility</a>.
</p></dd><dt id="SQL-CREATETABLE-UNLOGGED"><span class="term"><code class="literal">UNLOGGED</code></span></dt><dd><p>
If specified, the table is created as an unlogged table. Data written
to unlogged tables is not written to the write-ahead log (see <a class="xref" href="wal.html" title="Chapter 30. Reliability and the Write-Ahead Log">Chapter 30</a>), which makes them considerably faster than ordinary
tables. However, they are not crash-safe: an unlogged table is
automatically truncated after a crash or unclean shutdown. The contents
of an unlogged table are also not replicated to standby servers.
Any indexes created on an unlogged table are automatically unlogged as
well.
</p></dd><dt><span class="term"><code class="literal">IF NOT EXISTS</code></span></dt><dd><p>
Do not throw an error if a relation with the same name already exists.
A notice is issued in this case. Note that there is no guarantee that
the existing relation is anything like the one that would have been
created.
</p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em></span></dt><dd><p>
The name (optionally schema-qualified) of the table to be created.
</p></dd><dt><span class="term"><code class="literal">OF <em class="replaceable"><code>type_name</code></em></code></span></dt><dd><p>
Creates a <em class="firstterm">typed table</em>, which takes its
structure from the specified composite type (name optionally
schema-qualified). A typed table is tied to its type; for
example the table will be dropped if the type is dropped
(with <code class="literal">DROP TYPE ... CASCADE</code>).
</p><p>
When a typed table is created, then the data types of the
columns are determined by the underlying composite type and are
not specified by the <code class="literal">CREATE TABLE</code> command.
But the <code class="literal">CREATE TABLE</code> command can add defaults
and constraints to the table and can specify storage parameters.
</p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>
The name of a column to be created in the new table.
</p></dd><dt><span class="term"><em class="replaceable"><code>data_type</code></em></span></dt><dd><p>
The data type of the column. This can include array
specifiers. For more information on the data types supported by
<span class="productname">PostgreSQL</span>, refer to <a class="xref" href="datatype.html" title="Chapter 8. Data Types">Chapter 8</a>.
</p></dd><dt><span class="term"><code class="literal">COLLATE <em class="replaceable"><code>collation</code></em></code></span></dt><dd><p>
The <code class="literal">COLLATE</code> clause assigns a collation to
the column (which must be of a collatable data type).
If not specified, the column data type's default collation is used.
</p></dd><dt><span class="term"><code class="literal">INHERITS ( <em class="replaceable"><code>parent_table</code></em> [, ... ] )</code></span></dt><dd><p>
The optional <code class="literal">INHERITS</code> clause specifies a list of
tables from which the new table automatically inherits all
columns. Parent tables can be plain tables or foreign tables.
</p><p>
Use of <code class="literal">INHERITS</code> creates a persistent relationship
between the new child table and its parent table(s). Schema
modifications to the parent(s) normally propagate to children
as well, and by default the data of the child table is included in
scans of the parent(s).
</p><p>
If the same column name exists in more than one parent
table, an error is reported unless the data types of the columns
match in each of the parent tables. If there is no conflict,
then the duplicate columns are merged to form a single column in
the new table. If the column name list of the new table
contains a column name that is also inherited, the data type must
likewise match the inherited column(s), and the column
definitions are merged into one. If the
new table explicitly specifies a default value for the column,
this default overrides any defaults from inherited declarations
of the column. Otherwise, any parents that specify default
values for the column must all specify the same default, or an
error will be reported.
</p><p>
<code class="literal">CHECK</code> constraints are merged in essentially the same way as
columns: if multiple parent tables and/or the new table definition
contain identically-named <code class="literal">CHECK</code> constraints, these
constraints must all have the same check expression, or an error will be
reported. Constraints having the same name and expression will
be merged into one copy. A constraint marked <code class="literal">NO INHERIT</code> in a
parent will not be considered. Notice that an unnamed <code class="literal">CHECK</code>
constraint in the new table will never be merged, since a unique name
will always be chosen for it.
</p><p>
Column <code class="literal">STORAGE</code> settings are also copied from parent tables.
</p><p>
If a column in the parent table is an identity column, that property is
not inherited. A column in the child table can be declared identity
column if desired.
</p></dd><dt><span class="term"><code class="literal">PARTITION BY { RANGE | LIST | HASH } ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ <em class="replaceable"><code>opclass</code></em> ] [, ...] ) </code></span></dt><dd><p>
The optional <code class="literal">PARTITION BY</code> clause specifies a strategy
of partitioning the table. The table thus created is called a
<em class="firstterm">partitioned</em> table. The parenthesized list of
columns or expressions forms the <em class="firstterm">partition key</em>
for the table. When using range or hash partitioning, the partition key
can include multiple columns or expressions (up to 32, but this limit can
be altered when building <span class="productname">PostgreSQL</span>), but for
list partitioning, the partition key must consist of a single column or
expression.
</p><p>
Range and list partitioning require a btree operator class, while hash
partitioning requires a hash operator class. If no operator class is
specified explicitly, the default operator class of the appropriate
type will be used; if no default operator class exists, an error will
be raised. When hash partitioning is used, the operator class used
must implement support function 2 (see <a class="xref" href="xindex.html#XINDEX-SUPPORT" title="38.15.3. Index Method Support Routines">Section 38.15.3</a>
for details).
</p><p>
A partitioned table is divided into sub-tables (called partitions),
which are created using separate <code class="literal">CREATE TABLE</code> commands.
The partitioned table is itself empty. A data row inserted into the
table is routed to a partition based on the value of columns or
expressions in the partition key. If no existing partition matches
the values in the new row, an error will be reported.
</p><p>
Partitioned tables do not support <code class="literal">EXCLUDE</code> constraints;
however, you can define these constraints on individual partitions.
Also, while it's possible to define <code class="literal">PRIMARY KEY</code>
constraints on partitioned tables, creating foreign keys that
reference a partitioned table is not yet supported.
</p><p>
See <a class="xref" href="ddl-partitioning.html" title="5.10. Table Partitioning">Section 5.10</a> for more discussion on table
partitioning.
</p></dd><dt id="SQL-CREATETABLE-PARTITION"><span class="term"><code class="literal">PARTITION OF <em class="replaceable"><code>parent_table</code></em> { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }</code></span></dt><dd><p>
Creates the table as a <em class="firstterm">partition</em> of the specified
parent table. The table can be created either as a partition for specific
values using <code class="literal">FOR VALUES</code> or as a default partition
using <code class="literal">DEFAULT</code>. This option is not available for
hash-partitioned tables.
</p><p>
The <em class="replaceable"><code>partition_bound_spec</code></em>
must correspond to the partitioning method and partition key of the
parent table, and must not overlap with any existing partition of that
parent. The form with <code class="literal">IN</code> is used for list partitioning,
the form with <code class="literal">FROM</code> and <code class="literal">TO</code> is used
for range partitioning, and the form with <code class="literal">WITH</code> is used
for hash partitioning.
</p><p>
Each of the values specified in
the <em class="replaceable"><code>partition_bound_spec</code></em> is
a literal, <code class="literal">NULL</code>, <code class="literal">MINVALUE</code>, or
<code class="literal">MAXVALUE</code>. Each literal value must be either a
numeric constant that is coercible to the corresponding partition key
column's type, or a string literal that is valid input for that type.
</p><p>
When creating a list partition, <code class="literal">NULL</code> can be
specified to signify that the partition allows the partition key
column to be null. However, there cannot be more than one such
list partition for a given parent table. <code class="literal">NULL</code>
cannot be specified for range partitions.
</p><p>
When creating a range partition, the lower bound specified with
<code class="literal">FROM</code> is an inclusive bound, whereas the upper
bound specified with <code class="literal">TO</code> is an exclusive bound.
That is, the values specified in the <code class="literal">FROM</code> list
are valid values of the corresponding partition key columns for this
partition, whereas those in the <code class="literal">TO</code> list are
not. Note that this statement must be understood according to the
rules of row-wise comparison (<a class="xref" href="functions-comparisons.html#ROW-WISE-COMPARISON" title="9.23.5. Row Constructor Comparison">Section 9.23.5</a>).
For example, given <code class="literal">PARTITION BY RANGE (x,y)</code>, a partition
bound <code class="literal">FROM (1, 2) TO (3, 4)</code>
allows <code class="literal">x=1</code> with any <code class="literal">y>=2</code>,
<code class="literal">x=2</code> with any non-null <code class="literal">y</code>,
and <code class="literal">x=3</code> with any <code class="literal">y<4</code>.
</p><p>
The special values <code class="literal">MINVALUE</code> and <code class="literal">MAXVALUE</code>
may be used when creating a range partition to indicate that there
is no lower or upper bound on the column's value. For example, a
partition defined using <code class="literal">FROM (MINVALUE) TO (10)</code> allows
any values less than 10, and a partition defined using
<code class="literal">FROM (10) TO (MAXVALUE)</code> allows any values greater than
or equal to 10.
</p><p>
When creating a range partition involving more than one column, it
can also make sense to use <code class="literal">MAXVALUE</code> as part of the lower
bound, and <code class="literal">MINVALUE</code> as part of the upper bound. For
example, a partition defined using
<code class="literal">FROM (0, MAXVALUE) TO (10, MAXVALUE)</code> allows any rows
where the first partition key column is greater than 0 and less than
or equal to 10. Similarly, a partition defined using
<code class="literal">FROM ('a', MINVALUE) TO ('b', MINVALUE)</code> allows any rows
where the first partition key column starts with "a".
</p><p>
Note that if <code class="literal">MINVALUE</code> or <code class="literal">MAXVALUE</code> is used for
one column of a partitioning bound, the same value must be used for all
subsequent columns. For example, <code class="literal">(10, MINVALUE, 0)</code> is not
a valid bound; you should write <code class="literal">(10, MINVALUE, MINVALUE)</code>.
</p><p>
Also note that some element types, such as <code class="literal">timestamp</code>,
have a notion of "infinity", which is just another value that can
be stored. This is different from <code class="literal">MINVALUE</code> and
<code class="literal">MAXVALUE</code>, which are not real values that can be stored,
but rather they are ways of saying that the value is unbounded.
<code class="literal">MAXVALUE</code> can be thought of as being greater than any
other value, including "infinity" and <code class="literal">MINVALUE</code> as being
less than any other value, including "minus infinity". Thus the range
<code class="literal">FROM ('infinity') TO (MAXVALUE)</code> is not an empty range; it
allows precisely one value to be stored — "infinity".
</p><p>
If <code class="literal">DEFAULT</code> is specified, the table will be
created as a default partition of the parent table. The parent can
either be a list or range partitioned table. A partition key value
not fitting into any other partition of the given parent will be
routed to the default partition. There can be only one default
partition for a given parent table.
</p><p>
When a table has an existing <code class="literal">DEFAULT</code> partition and
a new partition is added to it, the existing default partition must
be scanned to verify that it does not contain any rows which properly
belong in the new partition. If the default partition contains a
large number of rows, this may be slow. The scan will be skipped if
the default partition is a foreign table or if it has a constraint which
proves that it cannot contain rows which should be placed in the new
partition.
</p><p>
When creating a hash partition, a modulus and remainder must be specified.
The modulus must be a positive integer, and the remainder must be a
non-negative integer less than the modulus. Typically, when initially
setting up a hash-partitioned table, you should choose a modulus equal to
the number of partitions and assign every table the same modulus and a
different remainder (see examples, below). However, it is not required
that every partition have the same modulus, only that every modulus which
occurs among the partitions of a hash-partitioned table is a factor of the
next larger modulus. This allows the number of partitions to be increased
incrementally without needing to move all the data at once. For example,
suppose you have a hash-partitioned table with 8 partitions, each of which
has modulus 8, but find it necessary to increase the number of partitions
to 16. You can detach one of the modulus-8 partitions, create two new
modulus-16 partitions covering the same portion of the key space (one with
a remainder equal to the remainder of the detached partition, and the
other with a remainder equal to that value plus 8), and repopulate them
with data. You can then repeat this -- perhaps at a later time -- for
each modulus-8 partition until none remain. While this may still involve
a large amount of data movement at each step, it is still better than
having to create a whole new table and move all the data at once.
</p><p>
A partition must have the same column names and types as the partitioned
table to which it belongs. If the parent is specified <code class="literal">WITH
OIDS</code> then all partitions must have OIDs; the parent's OID
column will be inherited by all partitions just like any other column.
Modifications to the column names or types of a partitioned table, or
the addition or removal of an OID column, will automatically propagate
to all partitions. <code class="literal">CHECK</code> constraints will be inherited
automatically by every partition, but an individual partition may specify
additional <code class="literal">CHECK</code> constraints; additional constraints with
the same name and condition as in the parent will be merged with the
parent constraint. Defaults may be specified separately for each
partition.
</p><p>
Rows inserted into a partitioned table will be automatically routed to
the correct partition. If no suitable partition exists, an error will
occur.
</p><p>
Operations such as TRUNCATE which normally affect a table and all of its
inheritance children will cascade to all partitions, but may also be
performed on an individual partition. Note that dropping a partition
with <code class="literal">DROP TABLE</code> requires taking an <code class="literal">ACCESS
EXCLUSIVE</code> lock on the parent table.
</p></dd><dt><span class="term"><code class="literal">LIKE <em class="replaceable"><code>source_table</code></em> [ <em class="replaceable"><code>like_option</code></em> ... ]</code></span></dt><dd><p>
The <code class="literal">LIKE</code> clause specifies a table from which
the new table automatically copies all column names, their data types,
and their not-null constraints.
</p><p>
Unlike <code class="literal">INHERITS</code>, the new table and original table
are completely decoupled after creation is complete. Changes to the
original table will not be applied to the new table, and it is not
possible to include data of the new table in scans of the original
table.
</p><p>
Default expressions for the copied column definitions will be copied
only if <code class="literal">INCLUDING DEFAULTS</code> is specified. The
default behavior is to exclude default expressions, resulting in the
copied columns in the new table having null defaults.
Note that copying defaults that call database-modification functions,
such as <code class="function">nextval</code>, may create a functional linkage between
the original and new tables.
</p><p>
Any identity specifications of copied column definitions will only be
copied if <code class="literal">INCLUDING IDENTITY</code> is specified. A new
sequence is created for each identity column of the new table, separate
from the sequences associated with the old table.
</p><p>
Not-null constraints are always copied to the new table.
<code class="literal">CHECK</code> constraints will be copied only if
<code class="literal">INCLUDING CONSTRAINTS</code> is specified.
No distinction is made between column constraints and table
constraints.
</p><p>
Extended statistics are copied to the new table if
<code class="literal">INCLUDING STATISTICS</code> is specified.
</p><p>
Indexes, <code class="literal">PRIMARY KEY</code>, <code class="literal">UNIQUE</code>,
and <code class="literal">EXCLUDE</code> constraints on the original table will be
created on the new table only if <code class="literal">INCLUDING INDEXES</code>
is specified. Names for the new indexes and constraints are
chosen according to the default rules, regardless of how the originals
were named. (This behavior avoids possible duplicate-name failures for
the new indexes.)
</p><p>
<code class="literal">STORAGE</code> settings for the copied column definitions will be
copied only if <code class="literal">INCLUDING STORAGE</code> is specified. The
default behavior is to exclude <code class="literal">STORAGE</code> settings, resulting
in the copied columns in the new table having type-specific default
settings. For more on <code class="literal">STORAGE</code> settings, see
<a class="xref" href="storage-toast.html" title="68.2. TOAST">Section 68.2</a>.
</p><p>
Comments for the copied columns, constraints, and indexes
will be copied only if <code class="literal">INCLUDING COMMENTS</code>
is specified. The default behavior is to exclude comments, resulting in
the copied columns and constraints in the new table having no comments.
</p><p>
<code class="literal">INCLUDING ALL</code> is an abbreviated form of
<code class="literal">INCLUDING COMMENTS INCLUDING CONSTRAINTS INCLUDING DEFAULTS INCLUDING IDENTITY INCLUDING INDEXES INCLUDING STATISTICS INCLUDING STORAGE</code>.
</p><p>
Note that unlike <code class="literal">INHERITS</code>, columns and
constraints copied by <code class="literal">LIKE</code> are not merged with similarly
named columns and constraints.
If the same name is specified explicitly or in another
<code class="literal">LIKE</code> clause, an error is signaled.
</p><p>
The <code class="literal">LIKE</code> clause can also be used to copy column
definitions from views, foreign tables, or composite types.
Inapplicable options (e.g., <code class="literal">INCLUDING INDEXES</code> from
a view) are ignored.
</p></dd><dt><span class="term"><code class="literal">CONSTRAINT <em class="replaceable"><code>constraint_name</code></em></code></span></dt><dd><p>
An optional name for a column or table constraint. If the
constraint is violated, the constraint name is present in error messages,
so constraint names like <code class="literal">col must be positive</code> can be used
to communicate helpful constraint information to client applications.
(Double-quotes are needed to specify constraint names that contain spaces.)
If a constraint name is not specified, the system generates a name.
</p></dd><dt><span class="term"><code class="literal">NOT NULL</code></span></dt><dd><p>
The column is not allowed to contain null values.
</p></dd><dt><span class="term"><code class="literal">NULL</code></span></dt><dd><p>
The column is allowed to contain null values. This is the default.
</p><p>
This clause is only provided for compatibility with
non-standard SQL databases. Its use is discouraged in new
applications.
</p></dd><dt><span class="term"><code class="literal">CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] </code></span></dt><dd><p>
The <code class="literal">CHECK</code> clause specifies an expression producing a
Boolean result which new or updated rows must satisfy for an
insert or update operation to succeed. Expressions evaluating
to TRUE or UNKNOWN succeed. Should any row of an insert or
update operation produce a FALSE result, an error exception is
raised and the insert or update does not alter the database. A
check constraint specified as a column constraint should
reference that column's value only, while an expression
appearing in a table constraint can reference multiple columns.
</p><p>
Currently, <code class="literal">CHECK</code> expressions cannot contain
subqueries nor refer to variables other than columns of the
current row. The system column <code class="literal">tableoid</code>
may be referenced, but not any other system column.
</p><p>
A constraint marked with <code class="literal">NO INHERIT</code> will not propagate to
child tables.
</p><p>
When a table has multiple <code class="literal">CHECK</code> constraints,
they will be tested for each row in alphabetical order by name,
after checking <code class="literal">NOT NULL</code> constraints.
(<span class="productname">PostgreSQL</span> versions before 9.5 did not honor any
particular firing order for <code class="literal">CHECK</code> constraints.)
</p></dd><dt><span class="term"><code class="literal">DEFAULT
<em class="replaceable"><code>default_expr</code></em></code></span></dt><dd><p>
The <code class="literal">DEFAULT</code> clause assigns a default data value for
the column whose column definition it appears within. The value
is any variable-free expression (subqueries and cross-references
to other columns in the current table are not allowed). The
data type of the default expression must match the data type of the
column.
</p><p>
The default expression will be used in any insert operation that
does not specify a value for the column. If there is no default
for a column, then the default is null.
</p></dd><dt><span class="term"><code class="literal">GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ]</code></span></dt><dd><p>
This clause creates the column as an <em class="firstterm">identity
column</em>. It will have an implicit sequence attached to it
and the column in new rows will automatically have values from the
sequence assigned to it.
</p><p>
The clauses <code class="literal">ALWAYS</code> and <code class="literal">BY DEFAULT</code>
determine how the sequence value is given precedence over a
user-specified value in an <code class="command">INSERT</code> statement.
If <code class="literal">ALWAYS</code> is specified, a user-specified value is
only accepted if the <code class="command">INSERT</code> statement
specifies <code class="literal">OVERRIDING SYSTEM VALUE</code>. If <code class="literal">BY
DEFAULT</code> is specified, then the user-specified value takes
precedence. See <a class="xref" href="sql-insert.html" title="INSERT"><span class="refentrytitle">INSERT</span></a> for details. (In
the <code class="command">COPY</code> command, user-specified values are always
used regardless of this setting.)
</p><p>
The optional <em class="replaceable"><code>sequence_options</code></em> clause can be
used to override the options of the sequence.
See <a class="xref" href="sql-createsequence.html" title="CREATE SEQUENCE"><span class="refentrytitle">CREATE SEQUENCE</span></a> for details.
</p></dd><dt><span class="term"><code class="literal">UNIQUE</code> (column constraint)<br /></span><span class="term"><code class="literal">UNIQUE ( <em class="replaceable"><code>column_name</code></em> [, ... ] )</code>
[<span class="optional"> INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ...]) </span>] (table constraint)</span></dt><dd><p>
The <code class="literal">UNIQUE</code> constraint specifies that a
group of one or more columns of a table can contain
only unique values. The behavior of the unique table constraint
is the same as that for column constraints, with the additional
capability to span multiple columns.
</p><p>
For the purpose of a unique constraint, null values are not
considered equal.
</p><p>
Each unique table constraint must name a set of columns that is
different from the set of columns named by any other unique or
primary key constraint defined for the table. (Otherwise it
would just be the same constraint listed twice.)
</p><p>
When establishing a unique constraint for a multi-level partition
hierarchy, all the columns in the partition key of the target
partitioned table, as well as those of all its descendant partitioned
tables, must be included in the constraint definition.
</p><p>
Adding a unique constraint will automatically create a unique btree
index on the column or group of columns used in the constraint.
The optional clause <code class="literal">INCLUDE</code> adds to that index
one or more columns on which the uniqueness is not enforced.
Note that although the constraint is not enforced on the included columns,
it still depends on them. Consequently, some operations on these columns
(e.g. <code class="literal">DROP COLUMN</code>) can cause cascaded constraint and
index deletion.
</p></dd><dt><span class="term"><code class="literal">PRIMARY KEY</code> (column constraint)<br /></span><span class="term"><code class="literal">PRIMARY KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] )</code>
[<span class="optional"> INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ...]) </span>] (table constraint)</span></dt><dd><p>
The <code class="literal">PRIMARY KEY</code> constraint specifies that a column or
columns of a table can contain only unique (non-duplicate), nonnull
values. Only one primary key can be specified for a table, whether as a
column constraint or a table constraint.
</p><p>
The primary key constraint should name a set of columns that is
different from the set of columns named by any unique
constraint defined for the same table. (Otherwise, the unique
constraint is redundant and will be discarded.)
</p><p>
<code class="literal">PRIMARY KEY</code> enforces the same data constraints as
a combination of <code class="literal">UNIQUE</code> and <code class="literal">NOT NULL</code>, but
identifying a set of columns as the primary key also provides metadata
about the design of the schema, since a primary key implies that other
tables can rely on this set of columns as a unique identifier for rows.
</p><p>
<code class="literal">PRIMARY KEY</code> constraints share the restrictions that
<code class="literal">UNIQUE</code> constraints have when placed on partitioned
tables.
</p><p>
Adding a <code class="literal">PRIMARY KEY</code> constraint will automatically
create a unique btree index on the column or group of columns used in the
constraint. The optional <code class="literal">INCLUDE</code> clause allows a list
of columns to be specified which will be included in the non-key portion
of the index. Although uniqueness is not enforced on the included columns,
the constraint still depends on them. Consequently, some operations on the
included columns (e.g. <code class="literal">DROP COLUMN</code>) can cause cascaded
constraint and index deletion.
</p></dd><dt id="SQL-CREATETABLE-EXCLUDE"><span class="term"><code class="literal">EXCLUDE [ USING <em class="replaceable"><code>index_method</code></em> ] ( <em class="replaceable"><code>exclude_element</code></em> WITH <em class="replaceable"><code>operator</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> [ WHERE ( <em class="replaceable"><code>predicate</code></em> ) ]</code></span></dt><dd><p>
The <code class="literal">EXCLUDE</code> clause defines an exclusion
constraint, which guarantees that if
any two rows are compared on the specified column(s) or
expression(s) using the specified operator(s), not all of these
comparisons will return <code class="literal">TRUE</code>. If all of the
specified operators test for equality, this is equivalent to a
<code class="literal">UNIQUE</code> constraint, although an ordinary unique constraint
will be faster. However, exclusion constraints can specify
constraints that are more general than simple equality.
For example, you can specify a constraint that
no two rows in the table contain overlapping circles
(see <a class="xref" href="datatype-geometric.html" title="8.8. Geometric Types">Section 8.8</a>) by using the
<code class="literal">&&</code> operator.
</p><p>
Exclusion constraints are implemented using
an index, so each specified operator must be associated with an
appropriate operator class
(see <a class="xref" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Section 11.10</a>) for the index access
method <em class="replaceable"><code>index_method</code></em>.
The operators are required to be commutative.
Each <em class="replaceable"><code>exclude_element</code></em>
can optionally specify an operator class and/or ordering options;
these are described fully under
<a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>.
</p><p>
The access method must support <code class="literal">amgettuple</code> (see <a class="xref" href="indexam.html" title="Chapter 61. Index Access Method Interface Definition">Chapter 61</a>); at present this means <acronym class="acronym">GIN</acronym>
cannot be used. Although it's allowed, there is little point in using
B-tree or hash indexes with an exclusion constraint, because this
does nothing that an ordinary unique constraint doesn't do better.
So in practice the access method will always be <acronym class="acronym">GiST</acronym> or
<acronym class="acronym">SP-GiST</acronym>.
</p><p>
The <em class="replaceable"><code>predicate</code></em> allows you to specify an
exclusion constraint on a subset of the table; internally this creates a
partial index. Note that parentheses are required around the predicate.
</p></dd><dt><span class="term"><code class="literal">REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> ) ] [ MATCH <em class="replaceable"><code>matchtype</code></em> ] [ ON DELETE <em class="replaceable"><code>action</code></em> ] [ ON UPDATE <em class="replaceable"><code>action</code></em> ]</code> (column constraint)<br /></span><span class="term"><code class="literal">FOREIGN KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] )
REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> [, ... ] ) ]
[ MATCH <em class="replaceable"><code>matchtype</code></em> ]
[ ON DELETE <em class="replaceable"><code>action</code></em> ]
[ ON UPDATE <em class="replaceable"><code>action</code></em> ]</code>
(table constraint)</span></dt><dd><p>
These clauses specify a foreign key constraint, which requires
that a group of one or more columns of the new table must only
contain values that match values in the referenced
column(s) of some row of the referenced table. If the <em class="replaceable"><code>refcolumn</code></em> list is omitted, the
primary key of the <em class="replaceable"><code>reftable</code></em>
is used. The referenced columns must be the columns of a non-deferrable
unique or primary key constraint in the referenced table. The user
must have <code class="literal">REFERENCES</code> permission on the referenced table
(either the whole table, or the specific referenced columns). The
addition of a foreign key constraint requires a
<code class="literal">SHARE ROW EXCLUSIVE</code> lock on the referenced table.
Note that foreign key constraints cannot be defined between temporary
tables and permanent tables. Also note that while it is possible to
define a foreign key on a partitioned table, it is not possible to
declare a foreign key that references a partitioned table.
</p><p>
A value inserted into the referencing column(s) is matched against the
values of the referenced table and referenced columns using the
given match type. There are three match types: <code class="literal">MATCH
FULL</code>, <code class="literal">MATCH PARTIAL</code>, and <code class="literal">MATCH
SIMPLE</code> (which is the default). <code class="literal">MATCH
FULL</code> will not allow one column of a multicolumn foreign key
to be null unless all foreign key columns are null; if they are all
null, the row is not required to have a match in the referenced table.
<code class="literal">MATCH SIMPLE</code> allows any of the foreign key columns
to be null; if any of them are null, the row is not required to have a
match in the referenced table.
<code class="literal">MATCH PARTIAL</code> is not yet implemented.
(Of course, <code class="literal">NOT NULL</code> constraints can be applied to the
referencing column(s) to prevent these cases from arising.)
</p><p>
In addition, when the data in the referenced columns is changed,
certain actions are performed on the data in this table's
columns. The <code class="literal">ON DELETE</code> clause specifies the
action to perform when a referenced row in the referenced table is
being deleted. Likewise, the <code class="literal">ON UPDATE</code>
clause specifies the action to perform when a referenced column
in the referenced table is being updated to a new value. If the
row is updated, but the referenced column is not actually
changed, no action is done. Referential actions other than the
<code class="literal">NO ACTION</code> check cannot be deferred, even if
the constraint is declared deferrable. There are the following possible
actions for each clause:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">NO ACTION</code></span></dt><dd><p>
Produce an error indicating that the deletion or update
would create a foreign key constraint violation.
If the constraint is deferred, this
error will be produced at constraint check time if there still
exist any referencing rows. This is the default action.
</p></dd><dt><span class="term"><code class="literal">RESTRICT</code></span></dt><dd><p>
Produce an error indicating that the deletion or update
would create a foreign key constraint violation.
This is the same as <code class="literal">NO ACTION</code> except that
the check is not deferrable.
</p></dd><dt><span class="term"><code class="literal">CASCADE</code></span></dt><dd><p>
Delete any rows referencing the deleted row, or update the
values of the referencing column(s) to the new values of the
referenced columns, respectively.
</p></dd><dt><span class="term"><code class="literal">SET NULL</code></span></dt><dd><p>
Set the referencing column(s) to null.
</p></dd><dt><span class="term"><code class="literal">SET DEFAULT</code></span></dt><dd><p>
Set the referencing column(s) to their default values.
(There must be a row in the referenced table matching the default
values, if they are not null, or the operation will fail.)
</p></dd></dl></div><p>
</p><p>
If the referenced column(s) are changed frequently, it might be wise to
add an index to the referencing column(s) so that referential actions
associated with the foreign key constraint can be performed more
efficiently.
</p></dd><dt><span class="term"><code class="literal">DEFERRABLE</code><br /></span><span class="term"><code class="literal">NOT DEFERRABLE</code></span></dt><dd><p>
This controls whether the constraint can be deferred. A
constraint that is not deferrable will be checked immediately
after every command. Checking of constraints that are
deferrable can be postponed until the end of the transaction
(using the <a class="xref" href="sql-set-constraints.html" title="SET CONSTRAINTS"><span class="refentrytitle">SET CONSTRAINTS</span></a> command).
<code class="literal">NOT DEFERRABLE</code> is the default.
Currently, only <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>,
<code class="literal">EXCLUDE</code>, and
<code class="literal">REFERENCES</code> (foreign key) constraints accept this
clause. <code class="literal">NOT NULL</code> and <code class="literal">CHECK</code> constraints are not
deferrable. Note that deferrable constraints cannot be used as
conflict arbitrators in an <code class="command">INSERT</code> statement that
includes an <code class="literal">ON CONFLICT DO UPDATE</code> clause.
</p></dd><dt><span class="term"><code class="literal">INITIALLY IMMEDIATE</code><br /></span><span class="term"><code class="literal">INITIALLY DEFERRED</code></span></dt><dd><p>
If a constraint is deferrable, this clause specifies the default
time to check the constraint. If the constraint is
<code class="literal">INITIALLY IMMEDIATE</code>, it is checked after each
statement. This is the default. If the constraint is
<code class="literal">INITIALLY DEFERRED</code>, it is checked only at the
end of the transaction. The constraint check time can be
altered with the <a class="xref" href="sql-set-constraints.html" title="SET CONSTRAINTS"><span class="refentrytitle">SET CONSTRAINTS</span></a> command.
</p></dd><dt><span class="term"><code class="literal">WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] )</code></span></dt><dd><p>
This clause specifies optional storage parameters for a table or index;
see <a class="xref" href="sql-createtable.html#SQL-CREATETABLE-STORAGE-PARAMETERS" title="Storage Parameters">Storage Parameters</a> for more
information. The <code class="literal">WITH</code> clause for a
table can also include <code class="literal">OIDS=TRUE</code> (or just <code class="literal">OIDS</code>)
to specify that rows of the new table
should have OIDs (object identifiers) assigned to them, or
<code class="literal">OIDS=FALSE</code> to specify that the rows should not have OIDs.
If <code class="literal">OIDS</code> is not specified, the default setting depends upon
the <a class="xref" href="runtime-config-compatible.html#GUC-DEFAULT-WITH-OIDS">default_with_oids</a> configuration parameter.
(If the new table inherits from any tables that have OIDs, then
<code class="literal">OIDS=TRUE</code> is forced even if the command says
<code class="literal">OIDS=FALSE</code>.)
</p><p>
If <code class="literal">OIDS=FALSE</code> is specified or implied, the new
table does not store OIDs and no OID will be assigned for a row inserted
into it. This is generally considered worthwhile, since it
will reduce OID consumption and thereby postpone the wraparound
of the 32-bit OID counter. Once the counter wraps around, OIDs
can no longer be assumed to be unique, which makes them
considerably less useful. In addition, excluding OIDs from a
table reduces the space required to store the table on disk by
4 bytes per row (on most machines), slightly improving performance.
</p><p>
To remove OIDs from a table after it has been created, use <a class="xref" href="sql-altertable.html" title="ALTER TABLE"><span class="refentrytitle">ALTER TABLE</span></a>.
</p></dd><dt><span class="term"><code class="literal">WITH OIDS</code><br /></span><span class="term"><code class="literal">WITHOUT OIDS</code></span></dt><dd><p>
These are obsolescent syntaxes equivalent to <code class="literal">WITH (OIDS)</code>
and <code class="literal">WITH (OIDS=FALSE)</code>, respectively. If you wish to give
both an <code class="literal">OIDS</code> setting and storage parameters, you must use
the <code class="literal">WITH ( ... )</code> syntax; see above.
</p></dd><dt><span class="term"><code class="literal">ON COMMIT</code></span></dt><dd><p>
The behavior of temporary tables at the end of a transaction
block can be controlled using <code class="literal">ON COMMIT</code>.
The three options are:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">PRESERVE ROWS</code></span></dt><dd><p>
No special action is taken at the ends of transactions.
This is the default behavior.
</p></dd><dt><span class="term"><code class="literal">DELETE ROWS</code></span></dt><dd><p>
All rows in the temporary table will be deleted at the end
of each transaction block. Essentially, an automatic <a class="xref" href="sql-truncate.html" title="TRUNCATE"><span class="refentrytitle">TRUNCATE</span></a> is done
at each commit. When used on a partitioned table, this
is not cascaded to its partitions.
</p></dd><dt><span class="term"><code class="literal">DROP</code></span></dt><dd><p>
The temporary table will be dropped at the end of the current
transaction block. When used on a partitioned table, this action
drops its partitions and when used on tables with inheritance
children, it drops the dependent children.
</p></dd></dl></div></dd><dt><span class="term"><code class="literal">TABLESPACE <em class="replaceable"><code>tablespace_name</code></em></code></span></dt><dd><p>
The <em class="replaceable"><code>tablespace_name</code></em> is the name
of the tablespace in which the new table is to be created.
If not specified,
<a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a> is consulted, or
<a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> if the table is temporary.
</p></dd><dt><span class="term"><code class="literal">USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em></code></span></dt><dd><p>
This clause allows selection of the tablespace in which the index
associated with a <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY
KEY</code>, or <code class="literal">EXCLUDE</code> constraint will be created.
If not specified,
<a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a> is consulted, or
<a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> if the table is temporary.
</p></dd></dl></div><div class="refsect2" id="SQL-CREATETABLE-STORAGE-PARAMETERS"><h3>Storage Parameters</h3><a id="id-1.9.3.85.6.3.2" class="indexterm"></a><p>
The <code class="literal">WITH</code> clause can specify <em class="firstterm">storage parameters</em>
for tables, and for indexes associated with a <code class="literal">UNIQUE</code>,
<code class="literal">PRIMARY KEY</code>, or <code class="literal">EXCLUDE</code> constraint.
Storage parameters for
indexes are documented in <a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>.
The storage parameters currently
available for tables are listed below. For many of these parameters, as
shown, there is an additional parameter with the same name prefixed with
<code class="literal">toast.</code>, which controls the behavior of the
table's secondary <acronym class="acronym">TOAST</acronym> table, if any
(see <a class="xref" href="storage-toast.html" title="68.2. TOAST">Section 68.2</a> for more information about TOAST).
If a table parameter value is set and the
equivalent <code class="literal">toast.</code> parameter is not, the TOAST table
will use the table's parameter value.
Specifying these parameters for partitioned tables is not supported,
but you may specify them for individual leaf partitions.
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">fillfactor</code> (<code class="type">integer</code>)</span></dt><dd><p>
The fillfactor for a table is a percentage between 10 and 100.
100 (complete packing) is the default. When a smaller fillfactor
is specified, <code class="command">INSERT</code> operations pack table pages only
to the indicated percentage; the remaining space on each page is
reserved for updating rows on that page. This gives <code class="command">UPDATE</code>
a chance to place the updated copy of a row on the same page as the
original, which is more efficient than placing it on a different page.
For a table whose entries are never updated, complete packing is the
best choice, but in heavily updated tables smaller fillfactors are
appropriate. This parameter cannot be set for TOAST tables.
</p></dd><dt><span class="term"><code class="literal">toast_tuple_target</code> (<code class="type">integer</code>)</span></dt><dd><p>
The toast_tuple_target specifies the minimum tuple length required before
we try to move long column values into TOAST tables, and is also the
target length we try to reduce the length below once toasting begins.
This only affects columns marked as either External or Extended
and applies only to new tuples - there is no effect on existing rows.
By default this parameter is set to allow at least 4 tuples per block,
which with the default blocksize will be 2040 bytes. Valid values are
between 128 bytes and the (blocksize - header), by default 8160 bytes.
Changing this value may not be useful for very short or very long rows.
Note that the default setting is often close to optimal, and
it is possible that setting this parameter could have negative
effects in some cases.
This parameter cannot be set for TOAST tables.
</p></dd><dt><span class="term"><code class="literal">parallel_workers</code> (<code class="type">integer</code>)</span></dt><dd><p>
This sets the number of workers that should be used to assist a parallel
scan of this table. If not set, the system will determine a value based
on the relation size. The actual number of workers chosen by the planner
or by utility statements that use parallel scans may be less, for example
due to the setting of <a class="xref" href="runtime-config-resource.html#GUC-MAX-WORKER-PROCESSES">max_worker_processes</a>.
</p></dd><dt><span class="term"><code class="literal">autovacuum_enabled</code>, <code class="literal">toast.autovacuum_enabled</code> (<code class="type">boolean</code>)</span></dt><dd><p>
Enables or disables the autovacuum daemon for a particular table.
If true, the autovacuum daemon will perform automatic <code class="command">VACUUM</code>
and/or <code class="command">ANALYZE</code> operations on this table following the rules
discussed in <a class="xref" href="routine-vacuuming.html#AUTOVACUUM" title="24.1.6. The Autovacuum Daemon">Section 24.1.6</a>.
If false, this table will not be autovacuumed, except to prevent
transaction ID wraparound. See <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="24.1.5. Preventing Transaction ID Wraparound Failures">Section 24.1.5</a> for
more about wraparound prevention.
Note that the autovacuum daemon does not run at all (except to prevent
transaction ID wraparound) if the <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM">autovacuum</a>
parameter is false; setting individual tables' storage parameters does
not override that. Therefore there is seldom much point in explicitly
setting this storage parameter to <code class="literal">true</code>, only
to <code class="literal">false</code>.
</p></dd><dt><span class="term"><code class="literal">autovacuum_vacuum_threshold</code>, <code class="literal">toast.autovacuum_vacuum_threshold</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-THRESHOLD">autovacuum_vacuum_threshold</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_vacuum_scale_factor</code>, <code class="literal">toast.autovacuum_vacuum_scale_factor</code> (<code class="type">float4</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-SCALE-FACTOR">autovacuum_vacuum_scale_factor</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_analyze_threshold</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-ANALYZE-THRESHOLD">autovacuum_analyze_threshold</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_analyze_scale_factor</code> (<code class="type">float4</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-ANALYZE-SCALE-FACTOR">autovacuum_analyze_scale_factor</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_vacuum_cost_delay</code>, <code class="literal">toast.autovacuum_vacuum_cost_delay</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-COST-DELAY">autovacuum_vacuum_cost_delay</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_vacuum_cost_limit</code>, <code class="literal">toast.autovacuum_vacuum_cost_limit</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-COST-LIMIT">autovacuum_vacuum_cost_limit</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_freeze_min_age</code>, <code class="literal">toast.autovacuum_freeze_min_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-MIN-AGE">vacuum_freeze_min_age</a>
parameter. Note that autovacuum will ignore
per-table <code class="literal">autovacuum_freeze_min_age</code> parameters that are
larger than half the
system-wide <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a> setting.
</p></dd><dt><span class="term"><code class="literal">autovacuum_freeze_max_age</code>, <code class="literal">toast.autovacuum_freeze_max_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a>
parameter. Note that autovacuum will ignore
per-table <code class="literal">autovacuum_freeze_max_age</code> parameters that are
larger than the system-wide setting (it can only be set smaller).
</p></dd><dt><span class="term"><code class="literal">autovacuum_freeze_table_age</code>, <code class="literal">toast.autovacuum_freeze_table_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-TABLE-AGE">vacuum_freeze_table_age</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">autovacuum_multixact_freeze_min_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_min_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-MULTIXACT-FREEZE-MIN-AGE">vacuum_multixact_freeze_min_age</a>
parameter. Note that autovacuum will ignore
per-table <code class="literal">autovacuum_multixact_freeze_min_age</code> parameters
that are larger than half the
system-wide <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a>
setting.
</p></dd><dt><span class="term"><code class="literal">autovacuum_multixact_freeze_max_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_max_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value
for <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a> parameter.
Note that autovacuum will ignore
per-table <code class="literal">autovacuum_multixact_freeze_max_age</code> parameters
that are larger than the system-wide setting (it can only be set
smaller).
</p></dd><dt><span class="term"><code class="literal">autovacuum_multixact_freeze_table_age</code>, <code class="literal">toast.autovacuum_multixact_freeze_table_age</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value
for <a class="xref" href="runtime-config-client.html#GUC-VACUUM-MULTIXACT-FREEZE-TABLE-AGE">vacuum_multixact_freeze_table_age</a> parameter.
</p></dd><dt><span class="term"><code class="literal">log_autovacuum_min_duration</code>, <code class="literal">toast.log_autovacuum_min_duration</code> (<code class="type">integer</code>)</span></dt><dd><p>
Per-table value for <a class="xref" href="runtime-config-autovacuum.html#GUC-LOG-AUTOVACUUM-MIN-DURATION">log_autovacuum_min_duration</a>
parameter.
</p></dd><dt><span class="term"><code class="literal">user_catalog_table</code> (<code class="type">boolean</code>)</span></dt><dd><p>
Declare the table as an additional catalog table for purposes of
logical replication. See
<a class="xref" href="logicaldecoding-output-plugin.html#LOGICALDECODING-CAPABILITIES" title="49.6.2. Capabilities">Section 49.6.2</a> for details.
This parameter cannot be set for TOAST tables.
</p></dd></dl></div></div></div><div class="refsect1" id="SQL-CREATETABLE-NOTES"><h2>Notes</h2><p>
Using OIDs in new applications is not recommended: where
possible, using an identity column or other sequence
generator as the table's primary key is preferred. However, if
your application does make use of OIDs to identify specific
rows of a table, it is recommended to create a unique constraint
on the <code class="structfield">oid</code> column of that table, to ensure that
OIDs in the table will indeed uniquely identify rows even after
counter wraparound. Avoid assuming that OIDs are unique across
tables; if you need a database-wide unique identifier, use the
combination of <code class="structfield">tableoid</code> and row OID for the
purpose.
</p><div class="tip"><h3 class="title">Tip</h3><p>
The use of <code class="literal">OIDS=FALSE</code> is not recommended
for tables with no primary key, since without either an OID or a
unique data key, it is difficult to identify specific rows.
</p></div><p>
<span class="productname">PostgreSQL</span> automatically creates an
index for each unique constraint and primary key constraint to
enforce uniqueness. Thus, it is not necessary to create an
index explicitly for primary key columns. (See <a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a> for more information.)
</p><p>
Unique constraints and primary keys are not inherited in the
current implementation. This makes the combination of
inheritance and unique constraints rather dysfunctional.
</p><p>
A table cannot have more than 1600 columns. (In practice, the
effective limit is usually lower because of tuple-length constraints.)
</p></div><div class="refsect1" id="SQL-CREATETABLE-EXAMPLES"><h2>Examples</h2><p>
Create table <code class="structname">films</code> and table
<code class="structname">distributors</code>:
</p><pre class="programlisting">
CREATE TABLE films (
code char(5) CONSTRAINT firstkey PRIMARY KEY,
title varchar(40) NOT NULL,
did integer NOT NULL,
date_prod date,
kind varchar(10),
len interval hour to minute
);
CREATE TABLE distributors (
did integer PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
name varchar(40) NOT NULL CHECK (name <> '')
);
</pre><p>
</p><p>
Create a table with a 2-dimensional array:
</p><pre class="programlisting">
CREATE TABLE array_int (
vector int[][]
);
</pre><p>
</p><p>
Define a unique table constraint for the table
<code class="literal">films</code>. Unique table constraints can be defined
on one or more columns of the table:
</p><pre class="programlisting">
CREATE TABLE films (
code char(5),
title varchar(40),
did integer,
date_prod date,
kind varchar(10),
len interval hour to minute,
CONSTRAINT production UNIQUE(date_prod)
);
</pre><p>
</p><p>
Define a check column constraint:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer CHECK (did > 100),
name varchar(40)
);
</pre><p>
</p><p>
Define a check table constraint:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer,
name varchar(40),
CONSTRAINT con1 CHECK (did > 100 AND name <> '')
);
</pre><p>
</p><p>
Define a primary key table constraint for the table
<code class="structname">films</code>:
</p><pre class="programlisting">
CREATE TABLE films (
code char(5),
title varchar(40),
did integer,
date_prod date,
kind varchar(10),
len interval hour to minute,
CONSTRAINT code_title PRIMARY KEY(code,title)
);
</pre><p>
</p><p>
Define a primary key constraint for table
<code class="structname">distributors</code>. The following two examples are
equivalent, the first using the table constraint syntax, the second
the column constraint syntax:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer,
name varchar(40),
PRIMARY KEY(did)
);
CREATE TABLE distributors (
did integer PRIMARY KEY,
name varchar(40)
);
</pre><p>
</p><p>
Assign a literal constant default value for the column
<code class="literal">name</code>, arrange for the default value of column
<code class="literal">did</code> to be generated by selecting the next value
of a sequence object, and make the default value of
<code class="literal">modtime</code> be the time at which the row is
inserted:
</p><pre class="programlisting">
CREATE TABLE distributors (
name varchar(40) DEFAULT 'Luso Films',
did integer DEFAULT nextval('distributors_serial'),
modtime timestamp DEFAULT current_timestamp
);
</pre><p>
</p><p>
Define two <code class="literal">NOT NULL</code> column constraints on the table
<code class="classname">distributors</code>, one of which is explicitly
given a name:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer CONSTRAINT no_null NOT NULL,
name varchar(40) NOT NULL
);
</pre><p>
</p><p>
Define a unique constraint for the <code class="literal">name</code> column:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer,
name varchar(40) UNIQUE
);
</pre><p>
The same, specified as a table constraint:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer,
name varchar(40),
UNIQUE(name)
);
</pre><p>
</p><p>
Create the same table, specifying 70% fill factor for both the table
and its unique index:
</p><pre class="programlisting">
CREATE TABLE distributors (
did integer,
name varchar(40),
UNIQUE(name) WITH (fillfactor=70)
)
WITH (fillfactor=70);
</pre><p>
</p><p>
Create table <code class="structname">circles</code> with an exclusion
constraint that prevents any two circles from overlapping:
</p><pre class="programlisting">
CREATE TABLE circles (
c circle,
EXCLUDE USING gist (c WITH &&)
);
</pre><p>
</p><p>
Create table <code class="structname">cinemas</code> in tablespace <code class="structname">diskvol1</code>:
</p><pre class="programlisting">
CREATE TABLE cinemas (
id serial,
name text,
location text
) TABLESPACE diskvol1;
</pre><p>
</p><p>
Create a composite type and a typed table:
</p><pre class="programlisting">
CREATE TYPE employee_type AS (name text, salary numeric);
CREATE TABLE employees OF employee_type (
PRIMARY KEY (name),
salary WITH OPTIONS DEFAULT 1000
);
</pre><p>
Create a range partitioned table:
</p><pre class="programlisting">
CREATE TABLE measurement (
logdate date not null,
peaktemp int,
unitsales int
) PARTITION BY RANGE (logdate);
</pre><p>
Create a range partitioned table with multiple columns in the partition key:
</p><pre class="programlisting">
CREATE TABLE measurement_year_month (
logdate date not null,
peaktemp int,
unitsales int
) PARTITION BY RANGE (EXTRACT(YEAR FROM logdate), EXTRACT(MONTH FROM logdate));
</pre><p>
Create a list partitioned table:
</p><pre class="programlisting">
CREATE TABLE cities (
city_id bigserial not null,
name text not null,
population bigint
) PARTITION BY LIST (left(lower(name), 1));
</pre><p>
Create a hash partitioned table:
</p><pre class="programlisting">
CREATE TABLE orders (
order_id bigint not null,
cust_id bigint not null,
status text
) PARTITION BY HASH (order_id);
</pre><p>
Create partition of a range partitioned table:
</p><pre class="programlisting">
CREATE TABLE measurement_y2016m07
PARTITION OF measurement (
unitsales DEFAULT 0
) FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
</pre><p>
Create a few partitions of a range partitioned table with multiple
columns in the partition key:
</p><pre class="programlisting">
CREATE TABLE measurement_ym_older
PARTITION OF measurement_year_month
FOR VALUES FROM (MINVALUE, MINVALUE) TO (2016, 11);
CREATE TABLE measurement_ym_y2016m11
PARTITION OF measurement_year_month
FOR VALUES FROM (2016, 11) TO (2016, 12);
CREATE TABLE measurement_ym_y2016m12
PARTITION OF measurement_year_month
FOR VALUES FROM (2016, 12) TO (2017, 01);
CREATE TABLE measurement_ym_y2017m01
PARTITION OF measurement_year_month
FOR VALUES FROM (2017, 01) TO (2017, 02);
</pre><p>
Create partition of a list partitioned table:
</p><pre class="programlisting">
CREATE TABLE cities_ab
PARTITION OF cities (
CONSTRAINT city_id_nonzero CHECK (city_id != 0)
) FOR VALUES IN ('a', 'b');
</pre><p>
Create partition of a list partitioned table that is itself further
partitioned and then add a partition to it:
</p><pre class="programlisting">
CREATE TABLE cities_ab
PARTITION OF cities (
CONSTRAINT city_id_nonzero CHECK (city_id != 0)
) FOR VALUES IN ('a', 'b') PARTITION BY RANGE (population);
CREATE TABLE cities_ab_10000_to_100000
PARTITION OF cities_ab FOR VALUES FROM (10000) TO (100000);
</pre><p>
Create partitions of a hash partitioned table:
</p><pre class="programlisting">
CREATE TABLE orders_p1 PARTITION OF orders
FOR VALUES WITH (MODULUS 4, REMAINDER 0);
CREATE TABLE orders_p2 PARTITION OF orders
FOR VALUES WITH (MODULUS 4, REMAINDER 1);
CREATE TABLE orders_p3 PARTITION OF orders
FOR VALUES WITH (MODULUS 4, REMAINDER 2);
CREATE TABLE orders_p4 PARTITION OF orders
FOR VALUES WITH (MODULUS 4, REMAINDER 3);
</pre><p>
Create a default partition:
</p><pre class="programlisting">
CREATE TABLE cities_partdef
PARTITION OF cities DEFAULT;
</pre></div><div class="refsect1" id="SQL-CREATETABLE-COMPATIBILITY"><h2>Compatibility</h2><p>
The <code class="command">CREATE TABLE</code> command conforms to the
<acronym class="acronym">SQL</acronym> standard, with exceptions listed below.
</p><div class="refsect2" id="id-1.9.3.85.9.3"><h3>Temporary Tables</h3><p>
Although the syntax of <code class="literal">CREATE TEMPORARY TABLE</code>
resembles that of the SQL standard, the effect is not the same. In the
standard,
temporary tables are defined just once and automatically exist (starting
with empty contents) in every session that needs them.
<span class="productname">PostgreSQL</span> instead
requires each session to issue its own <code class="literal">CREATE TEMPORARY
TABLE</code> command for each temporary table to be used. This allows
different sessions to use the same temporary table name for different
purposes, whereas the standard's approach constrains all instances of a
given temporary table name to have the same table structure.
</p><p>
The standard's definition of the behavior of temporary tables is
widely ignored. <span class="productname">PostgreSQL</span>'s behavior
on this point is similar to that of several other SQL databases.
</p><p>
The SQL standard also distinguishes between global and local temporary
tables, where a local temporary table has a separate set of contents for
each SQL module within each session, though its definition is still shared
across sessions. Since <span class="productname">PostgreSQL</span> does not
support SQL modules, this distinction is not relevant in
<span class="productname">PostgreSQL</span>.
</p><p>
For compatibility's sake, <span class="productname">PostgreSQL</span> will
accept the <code class="literal">GLOBAL</code> and <code class="literal">LOCAL</code> keywords
in a temporary table declaration, but they currently have no effect.
Use of these keywords is discouraged, since future versions of
<span class="productname">PostgreSQL</span> might adopt a more
standard-compliant interpretation of their meaning.
</p><p>
The <code class="literal">ON COMMIT</code> clause for temporary tables
also resembles the SQL standard, but has some differences.
If the <code class="literal">ON COMMIT</code> clause is omitted, SQL specifies that the
default behavior is <code class="literal">ON COMMIT DELETE ROWS</code>. However, the
default behavior in <span class="productname">PostgreSQL</span> is
<code class="literal">ON COMMIT PRESERVE ROWS</code>. The <code class="literal">ON COMMIT
DROP</code> option does not exist in SQL.
</p></div><div class="refsect2" id="id-1.9.3.85.9.4"><h3>Non-deferred Uniqueness Constraints</h3><p>
When a <code class="literal">UNIQUE</code> or <code class="literal">PRIMARY KEY</code> constraint is
not deferrable, <span class="productname">PostgreSQL</span> checks for
uniqueness immediately whenever a row is inserted or modified.
The SQL standard says that uniqueness should be enforced only at
the end of the statement; this makes a difference when, for example,
a single command updates multiple key values. To obtain
standard-compliant behavior, declare the constraint as
<code class="literal">DEFERRABLE</code> but not deferred (i.e., <code class="literal">INITIALLY
IMMEDIATE</code>). Be aware that this can be significantly slower than
immediate uniqueness checking.
</p></div><div class="refsect2" id="id-1.9.3.85.9.5"><h3>Column Check Constraints</h3><p>
The SQL standard says that <code class="literal">CHECK</code> column constraints
can only refer to the column they apply to; only <code class="literal">CHECK</code>
table constraints can refer to multiple columns.
<span class="productname">PostgreSQL</span> does not enforce this
restriction; it treats column and table check constraints alike.
</p></div><div class="refsect2" id="id-1.9.3.85.9.6"><h3><code class="literal">EXCLUDE</code> Constraint</h3><p>
The <code class="literal">EXCLUDE</code> constraint type is a
<span class="productname">PostgreSQL</span> extension.
</p></div><div class="refsect2" id="id-1.9.3.85.9.7"><h3><code class="literal">NULL</code> <span class="quote">“<span class="quote">Constraint</span>”</span></h3><p>
The <code class="literal">NULL</code> <span class="quote">“<span class="quote">constraint</span>”</span> (actually a
non-constraint) is a <span class="productname">PostgreSQL</span>
extension to the SQL standard that is included for compatibility with some
other database systems (and for symmetry with the <code class="literal">NOT
NULL</code> constraint). Since it is the default for any
column, its presence is simply noise.
</p></div><div class="refsect2" id="id-1.9.3.85.9.8"><h3>Constraint Naming</h3><p>
The SQL standard says that table and domain constraints must have names
that are unique across the schema containing the table or domain.
<span class="productname">PostgreSQL</span> is laxer: it only requires
constraint names to be unique across the constraints attached to a
particular table or domain. However, this extra freedom does not exist
for index-based constraints (<code class="literal">UNIQUE</code>,
<code class="literal">PRIMARY KEY</code>, and <code class="literal">EXCLUDE</code>
constraints), because the associated index is named the same as the
constraint, and index names must be unique across all relations within
the same schema.
</p><p>
Currently, <span class="productname">PostgreSQL</span> does not record names
for <code class="literal">NOT NULL</code> constraints at all, so they are not
subject to the uniqueness restriction. This might change in a future
release.
</p></div><div class="refsect2" id="id-1.9.3.85.9.9"><h3>Inheritance</h3><p>
Multiple inheritance via the <code class="literal">INHERITS</code> clause is
a <span class="productname">PostgreSQL</span> language extension.
SQL:1999 and later define single inheritance using a
different syntax and different semantics. SQL:1999-style
inheritance is not yet supported by
<span class="productname">PostgreSQL</span>.
</p></div><div class="refsect2" id="id-1.9.3.85.9.10"><h3>Zero-column Tables</h3><p>
<span class="productname">PostgreSQL</span> allows a table of no columns
to be created (for example, <code class="literal">CREATE TABLE foo();</code>). This
is an extension from the SQL standard, which does not allow zero-column
tables. Zero-column tables are not in themselves very useful, but
disallowing them creates odd special cases for <code class="command">ALTER TABLE
DROP COLUMN</code>, so it seems cleaner to ignore this spec restriction.
</p></div><div class="refsect2" id="id-1.9.3.85.9.11"><h3>Multiple Identity Columns</h3><p>
<span class="productname">PostgreSQL</span> allows a table to have more than one
identity column. The standard specifies that a table can have at most one
identity column. This is relaxed mainly to give more flexibility for
doing schema changes or migrations. Note that
the <code class="command">INSERT</code> command supports only one override clause
that applies to the entire statement, so having multiple identity columns
with different behaviors is not well supported.
</p></div><div class="refsect2" id="id-1.9.3.85.9.12"><h3><code class="literal">LIKE</code> Clause</h3><p>
While a <code class="literal">LIKE</code> clause exists in the SQL standard, many of the
options that <span class="productname">PostgreSQL</span> accepts for it are not
in the standard, and some of the standard's options are not implemented
by <span class="productname">PostgreSQL</span>.
</p></div><div class="refsect2" id="id-1.9.3.85.9.13"><h3><code class="literal">WITH</code> Clause</h3><p>
The <code class="literal">WITH</code> clause is a <span class="productname">PostgreSQL</span>
extension; neither storage parameters nor OIDs are in the standard.
</p></div><div class="refsect2" id="id-1.9.3.85.9.14"><h3>Tablespaces</h3><p>
The <span class="productname">PostgreSQL</span> concept of tablespaces is not
part of the standard. Hence, the clauses <code class="literal">TABLESPACE</code>
and <code class="literal">USING INDEX TABLESPACE</code> are extensions.
</p></div><div class="refsect2" id="id-1.9.3.85.9.15"><h3>Typed Tables</h3><p>
Typed tables implement a subset of the SQL standard. According to
the standard, a typed table has columns corresponding to the
underlying composite type as well as one other column that is
the <span class="quote">“<span class="quote">self-referencing column</span>”</span>. PostgreSQL does not
support these self-referencing columns explicitly, but the same
effect can be had using the OID feature.
</p></div><div class="refsect2" id="id-1.9.3.85.9.16"><h3><code class="literal">PARTITION BY</code> Clause</h3><p>
The <code class="literal">PARTITION BY</code> clause is a
<span class="productname">PostgreSQL</span> extension.
</p></div><div class="refsect2" id="id-1.9.3.85.9.17"><h3><code class="literal">PARTITION OF</code> Clause</h3><p>
The <code class="literal">PARTITION OF</code> clause is a
<span class="productname">PostgreSQL</span> extension.
</p></div></div><div class="refsect1" id="id-1.9.3.85.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-altertable.html" title="ALTER TABLE"><span class="refentrytitle">ALTER TABLE</span></a>, <a class="xref" href="sql-droptable.html" title="DROP TABLE"><span class="refentrytitle">DROP TABLE</span></a>, <a class="xref" href="sql-createtableas.html" title="CREATE TABLE AS"><span class="refentrytitle">CREATE TABLE AS</span></a>, <a class="xref" href="sql-createtablespace.html" title="CREATE TABLESPACE"><span class="refentrytitle">CREATE TABLESPACE</span></a>, <a class="xref" href="sql-createtype.html" title="CREATE TYPE"><span class="refentrytitle">CREATE TYPE</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createsubscription.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-createtableas.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE SUBSCRIPTION </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> CREATE TABLE AS</td></tr></table></div></body></html>
