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<!-- doc/src/sgml/func.sgml -->
<chapter id="functions">
<title>Functions and Operators</title>
<indexterm zone="functions">
<primary>function</primary>
</indexterm>
<indexterm zone="functions">
<primary>operator</primary>
</indexterm>
<para>
<productname>PostgreSQL</productname> provides a large number of
functions and operators for the built-in data types. This chapter
describes most of them, although additional special-purpose functions
appear in relevant sections of the manual. Users can also
define their own functions and operators, as described in
<xref linkend="server-programming"/>. The
<application>psql</application> commands <command>\df</command> and
<command>\do</command> can be used to list all
available functions and operators, respectively.
</para>
<para>
The notation used throughout this chapter to describe the argument and
result data types of a function or operator is like this:
<synopsis>
<function>repeat</function> ( <type>text</type>, <type>integer</type> ) <returnvalue>text</returnvalue>
</synopsis>
which says that the function <function>repeat</function> takes one text and
one integer argument and returns a result of type text. The right arrow
is also used to indicate the result of an example, thus:
<programlisting>
repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
</programlisting>
</para>
<para>
If you are concerned about portability then note that most of
the functions and operators described in this chapter, with the
exception of the most trivial arithmetic and comparison operators
and some explicitly marked functions, are not specified by the
<acronym>SQL</acronym> standard. Some of this extended functionality
is present in other <acronym>SQL</acronym> database management
systems, and in many cases this functionality is compatible and
consistent between the various implementations.
</para>
&func-logical;
&func-comparison;
&func-math;
&func-string;
&func-binarystring;
&func-bitstring;
&func-matching;
&func-formatting;
&func-datetime;
&func-enum;
&func-geometry;
&func-net;
&func-textsearch;
&func-uuid;
&func-xml;
&func-json;
&func-sequence;
&func-conditional;
&func-array;
&func-range;
&func-aggregate;
&func-window;
&func-merge-support;
&func-subquery;
&func-comparisons;
&func-srf;
&func-info;
&func-admin;
&func-trigger;
&func-event-triggers;
&func-statistics;
</chapter>
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