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427 lines
10 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.48 2000/08/29 20:02:09 momjian Exp $
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Postgres documentation
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-->
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<refentry id="SQL-SET">
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<refmeta>
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<refentrytitle id="SQL-SET-TITLE">SET</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>SET</refname>
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<refpurpose>Set run-time parameters</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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SET <replaceable class="PARAMETER">variable</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
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SET TIME ZONE { '<replaceable class="PARAMETER">timezone</replaceable>' | LOCAL | DEFAULT }
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</synopsis>
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<refsect2 id="R2-SQL-SET-1">
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<title>Inputs</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">variable</replaceable></term>
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<listitem>
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<para>
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A settable run-time parameter.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="PARAMETER">value</replaceable></term>
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<listitem>
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<para>
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New value of parameter. <option>DEFAULT</option> can be
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used to specify resetting the parameter to its default
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value. Lists of strings are allowed, but more complex
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constructs may need to be single or double quoted.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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</refsynopsisdiv>
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<refsect1 id="R1-SQL-SET-1">
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<title>Description</title>
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<para>
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The <command>SET</command> command changes run-time configuration
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parameters. The following parameters can be altered:
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<variablelist>
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<varlistentry>
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<term>CLIENT_ENCODING</term>
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<term>NAMES</term>
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<listitem>
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<para>
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Sets the multi-byte client encoding. The specified encoding
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must be supported by the backend.
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</para>
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<para>
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This option is only available if
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<productname>Postgres</productname> is build with multibyte
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support.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>DATESTYLE</term>
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<listitem>
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<para>
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Choose the date/time representation style. Two separate
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settings are made: the default date/time output and the
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interpretation of ambiguous input.
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</para>
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<para>
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The following are date/time output styles:
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<variablelist>
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<varlistentry>
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<term>ISO</term>
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<listitem>
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<para>
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Use ISO 8601-style dates and times (<literal>YYYY-MM-DD
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HH:MM:SS</literal>). This is the default.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SQL</term>
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<listitem>
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<para>
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Use Oracle/Ingres-style dates and times. Note that this
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style has nothing to do with SQL (which mandates ISO 8601
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style), the naming of this option is a historical accident.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Postgres</term>
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<listitem>
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<para>
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Use traditional <productname>Postgres</productname> format.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>German</term>
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<listitem>
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<para>
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Use <literal>dd.mm.yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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The following two options determine both a substyle of the
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<quote>SQL</quote> and <quote>Postgres</quote> output formats
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and the preferred interpretation of ambiguous date input.
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<variablelist>
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<varlistentry>
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<term>European</term>
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<listitem>
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<para>
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Use <literal>dd/mm/yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>NonEuropean</term>
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<term>US</term>
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<listitem>
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<para>
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Use <literal>mm/dd/yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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A value for <command>SET DATESTYLE</command> can be one from
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the first list (output styles), or one from the second list
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(substyles), or one from each separated by a comma.
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</para>
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<para>
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Date format initialization may be done by:
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<simplelist>
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<member>
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Setting the <envar>PGDATESTYLE</envar> environment variable.
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If PGDATESTYLE is set in the frontend environment of a client
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based on libpq, libpq will automatically set DATESTYLE to the
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value of PGDATESTYLE during connection start-up.
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</member>
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<member>
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Running postmaster using the option <option>-o -e</option> to
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set dates to the <literal>European</literal> convention.
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</member>
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</simplelist>
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</para>
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<para>
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The <option>DateStyle</option> option is really only intended
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for porting applications. To format your date/time values to
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choice, use the <function>to_char</function> family of
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functions.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SEED</term>
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<listitem>
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<para>
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Sets the internal seed for the random number generator.
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<variablelist>
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<varlistentry>
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<term><replaceable class="parameter">value</replaceable></term>
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<listitem>
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<para>
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The value for the seed to be used by the
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<function>random</function> function. Allowed
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values are floating point numbers between 0 and 1, which
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are then multiplied by 2^31-1. This product will
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silently overflow if a number outside the range is used.
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</para>
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<para>
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The seed can also be set by invoking the
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<function>setseed</function> SQL function:
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<programlisting>
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SELECT setseed(<replaceable>value</replaceable>);
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SERVER_ENCODING</term>
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<listitem>
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<para>
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Sets the multi-byte server encoding.
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</para>
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<para>
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This option is only available if
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<productname>Postgres</productname> was built with multibyte
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support.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>TIME ZONE</term>
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<term>TIMEZONE</term>
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<listitem>
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<para>
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The possible values for timezone depends on your operating
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system. For example, on Linux
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<filename>/usr/share/zoneinfo</filename> contains the database
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of time zones.
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</para>
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<para>
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Here are some valid values for timezone:
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<variablelist>
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<varlistentry>
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<term>PST8PDT</term>
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<listitem>
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<para>
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Set the time zone for California.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Portugal</term>
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<listitem>
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<para>
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Set time zone for Portugal.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>'Europe/Rome'</term>
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<listitem>
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<para>
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Set time zone for Italy.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>LOCAL</term>
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<term>DEFAULT</term>
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<listitem>
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<para>
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Set the time zone to your local time zone (the one that
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your operating system defaults to).
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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If an invalid time zone is specified, the time zone
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becomes GMT (on most systems anyway).
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</para>
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<para>
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If the PGTZ environment variable is set in the frontend
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environment of a client based on libpq, libpq will automatically
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set TIMEZONE to the value of PGTZ during connection start-up.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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An extended list of other run-time parameters can be found in the
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<citetitle>Administrator's Guide</citetitle>.
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</para>
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<para>
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Use <xref linkend="SQL-SHOW" endterm="SQL-SHOW-title"> to show the
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current setting of a parameters.
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</para>
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</refsect1>
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<refsect1>
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<title>Diagnostics</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><computeroutput>SET VARIABLE</computeroutput></term>
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<listitem>
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<para>
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Message returned if successful.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><computeroutput>ERROR: not a valid option name: <replaceable>name</replaceable></computeroutput></term>
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<listitem>
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<para>
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The parameter you tried to set does not exist.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><computeroutput>ERROR: permission denied</computeroutput></term>
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<listitem>
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<para>
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You must be a superuser to have access to certain settings.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><computeroutput>ERROR: <replaceable>name</replaceable> can only be set at start-up</computeroutput></term>
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<listitem>
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<para>
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Some parameters are fixed once the server is started.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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Set the style of date to traditional Postgres with European conventions:
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<screen>
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SET DATESTYLE TO Postgres,European;
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</screen>
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Set the timezone for Berkeley, California, using double quotes to
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preserve the uppercase attributes of the time zone specifier (note
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that the date/time format is ISO here):
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<screen>
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SET TIME ZONE "PST8PDT";
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SELECT CURRENT_TIMESTAMP AS today;
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today
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------------------------
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1998-03-31 07:41:21-08
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</screen>
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Set the timezone for Italy (note the required single or double quotes to handle
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the special characters):
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<screen>
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SET TIME ZONE 'Europe/Rome';
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SELECT CURRENT_TIMESTAMP AS today;
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today
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------------------------
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1998-03-31 17:41:31+02
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</screen>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-SET-3">
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<title>Compatibility</title>
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<refsect2 id="R2-SQL-SET-4">
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<title>
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SQL92
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</title>
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<para>
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The second syntax shown above (<literal>SET TIME ZONE</literal>)
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attempts to mimic <acronym>SQL92</acronym>. However, SQL allows
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only numeric time zone offsets. All other parameter settings as
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well as the first syntax shown above are a
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<productname>Postgres</productname> extension.
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</para>
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</refsect2>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode:sgml
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sgml-omittag:nil
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:("/usr/lib/sgml/catalog")
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sgml-local-ecat-files:nil
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End:
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