<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Enumerated Types</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.6.17 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Data Types" HREF="datatype.html"><LINK REL="PREVIOUS" TITLE="Boolean Type" HREF="datatype-boolean.html"><LINK REL="NEXT" TITLE="Geometric Types" HREF="datatype-geometric.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2020-02-15T12:30:38"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="4" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.6.17 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Boolean Type" HREF="datatype-boolean.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="datatype.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 8. Data Types</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Geometric Types" HREF="datatype-geometric.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="DATATYPE-ENUM" >8.7. Enumerated Types</A ></H1 ><P > Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the <TT CLASS="TYPE" >enum</TT > types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN6964" >8.7.1. Declaration of Enumerated Types</A ></H2 ><P > Enum types are created using the <A HREF="sql-createtype.html" >CREATE TYPE</A > command, for example: </P><PRE CLASS="PROGRAMLISTING" >CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');</PRE ><P> Once created, the enum type can be used in table and function definitions much like any other type: </P><PRE CLASS="PROGRAMLISTING" >CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy'); CREATE TABLE person ( name text, current_mood mood ); INSERT INTO person VALUES ('Moe', 'happy'); SELECT * FROM person WHERE current_mood = 'happy'; name | current_mood ------+-------------- Moe | happy (1 row)</PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN6970" >8.7.2. Ordering</A ></H2 ><P > The ordering of the values in an enum type is the order in which the values were listed when the type was created. All standard comparison operators and related aggregate functions are supported for enums. For example: </P><PRE CLASS="PROGRAMLISTING" >INSERT INTO person VALUES ('Larry', 'sad'); INSERT INTO person VALUES ('Curly', 'ok'); SELECT * FROM person WHERE current_mood > 'sad'; name | current_mood -------+-------------- Moe | happy Curly | ok (2 rows) SELECT * FROM person WHERE current_mood > 'sad' ORDER BY current_mood; name | current_mood -------+-------------- Curly | ok Moe | happy (2 rows) SELECT name FROM person WHERE current_mood = (SELECT MIN(current_mood) FROM person); name ------- Larry (1 row)</PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN6974" >8.7.3. Type Safety</A ></H2 ><P > Each enumerated data type is separate and cannot be compared with other enumerated types. See this example: </P><PRE CLASS="PROGRAMLISTING" >CREATE TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic'); CREATE TABLE holidays ( num_weeks integer, happiness happiness ); INSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy'); INSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy'); INSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic'); INSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad'); ERROR: invalid input value for enum happiness: "sad" SELECT person.name, holidays.num_weeks FROM person, holidays WHERE person.current_mood = holidays.happiness; ERROR: operator does not exist: mood = happiness</PRE ><P> </P ><P > If you really need to do something like that, you can either write a custom operator or add explicit casts to your query: </P><PRE CLASS="PROGRAMLISTING" >SELECT person.name, holidays.num_weeks FROM person, holidays WHERE person.current_mood::text = holidays.happiness::text; name | num_weeks ------+----------- Moe | 4 (1 row) </PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN6980" >8.7.4. Implementation Details</A ></H2 ><P > Enum labels are case sensitive, so <TT CLASS="TYPE" >'happy'</TT > is not the same as <TT CLASS="TYPE" >'HAPPY'</TT >. White space in the labels is significant too. </P ><P > Although enum types are primarily intended for static sets of values, there is support for adding new values to an existing enum type, and for renaming values (see <A HREF="sql-altertype.html" >ALTER TYPE</A >). Existing values cannot be removed from an enum type, nor can the sort ordering of such values be changed, short of dropping and re-creating the enum type. </P ><P > An enum value occupies four bytes on disk. The length of an enum value's textual label is limited by the <TT CLASS="SYMBOL" >NAMEDATALEN</TT > setting compiled into <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN >; in standard builds this means at most 63 bytes. </P ><P > The translations from internal enum values to textual labels are kept in the system catalog <A HREF="catalog-pg-enum.html" ><TT CLASS="STRUCTNAME" >pg_enum</TT ></A >. Querying this catalog directly can be useful. </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="datatype-boolean.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="datatype-geometric.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Boolean Type</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="datatype.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Geometric Types</TD ></TR ></TABLE ></DIV ></BODY ></HTML >