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2a5b6a7c9b
makes a few more small improvements to runtime.sgml, and makes some SGML conventions more consistent. Neil Conway
189 lines
5.2 KiB
Plaintext
189 lines
5.2 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/update.sgml,v 1.25 2003/09/11 21:42:20 momjian Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-UPDATE">
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<refmeta>
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<refentrytitle id="SQL-UPDATE-TITLE">UPDATE</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>UPDATE</refname>
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<refpurpose>update rows of a table</refpurpose>
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</refnamediv>
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<indexterm zone="sql-update">
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<primary>UPDATE</primary>
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</indexterm>
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<refsynopsisdiv>
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<synopsis>
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UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...]
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[ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
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[ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>UPDATE</command> changes the values of the specified
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columns in all rows that satisfy the condition. Only the columns to
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be modified need be mentioned in the statement; columns not explicitly
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<literal>SET</> retain their previous values.
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</para>
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<para>
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By default, <command>UPDATE</command> will update rows in the
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specified table and all its subtables. If you wish to only update
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the specific table mentioned, you must use the <literal>ONLY</>
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clause.
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</para>
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<para>
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You must have the <literal>UPDATE</literal> privilege on the table
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to update it, as well as the <literal>SELECT</literal>
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privilege to any table whose values are read in the
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<replaceable class="parameter">expression</replaceable>s or
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<replaceable class="parameter">condition</replaceable>.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">table</replaceable></term>
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<listitem>
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<para>
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The name (optionally schema-qualified) of the table to update.
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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">column</replaceable></term>
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<listitem>
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<para>
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The name of a column in <replaceable class="PARAMETER">table</replaceable>.
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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">expression</replaceable></term>
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<listitem>
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<para>
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An expression to assign to the column. The expression may use the
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old values of this and other columns in the table.
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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><literal>DEFAULT</literal></term>
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<listitem>
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<para>
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Set the column to its default value (which will be NULL if no
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specific default expression has been assigned to it).
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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">fromlist</replaceable></term>
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<listitem>
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<para>
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A list of table expressions, allowing columns from other tables
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to appear in the <literal>WHERE</> condition and the update expressions.
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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">condition</replaceable></term>
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<listitem>
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<para>
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An expression that returns a value of type <type>boolean</type>.
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Only rows for which this expression returns <literal>true</>
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will be updated.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Diagnostics</title>
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<variablelist>
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<varlistentry>
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<term><computeroutput>UPDATE <replaceable class="parameter">count</replaceable></computeroutput></term>
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<listitem>
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<para>
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Message returned if successful. The value <replaceable
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class="parameter">count</replaceable> is the number of rows
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updated. If <replaceable class="parameter">count</replaceable>
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is 0, no rows were updated.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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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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Change the word <literal>Drama</> to <literal>Dramatic</> in the
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column <structfield>kind</> of the table <literal>films</literal>:
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<programlisting>
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UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama';
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</programlisting>
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</para>
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<para>
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Adjust temperature entries and reset precipitation to its default
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value in one row of the table <literal>weather</literal>:
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<programlisting>
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UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
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WHERE city = 'San Francisco' AND date = '2003-07-03';
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</programlisting>
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</para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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This command conforms to the SQL standard. The
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<literal>FROM</literal> clause is a
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<productname>PostgreSQL</productname> extension.
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</para>
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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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-->
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