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doc/src/sgml/ref/drop_aggregate.sgml
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Peter Eisentraut
Convert documentation to DocBook XML
23 ноя 2017, 17:44
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<!--
doc/src/sgml/ref/drop_aggregate.sgml
PostgreSQL documentation
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<refentry id="sql-dropaggregate">
 <indexterm zone="sql-dropaggregate">
  <primary>DROP AGGREGATE</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>DROP AGGREGATE</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>DROP AGGREGATE</refname>
  <refpurpose>remove an aggregate function</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
DROP AGGREGATE [ IF EXISTS ] <replaceable>name</replaceable> ( <replaceable>aggregate_signature</replaceable> ) [, ...] [ CASCADE | RESTRICT ]

<phrase>where <replaceable>aggregate_signature</replaceable> is:</phrase>

* |
[ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ] |
[ [ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ] ] ORDER BY [ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>DROP AGGREGATE</command> removes an existing
   aggregate function. To execute this command the current
   user must be the owner of the aggregate function.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>

   <varlistentry>
    <term><literal>IF EXISTS</literal></term>
    <listitem>
     <para>
      Do not throw an error if the aggregate does not exist. A notice is issued
      in this case.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing aggregate function.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argmode</replaceable></term>

    <listitem>
     <para>
      The mode of an argument: <literal>IN</literal> or <literal>VARIADIC</literal>.
      If omitted, the default is <literal>IN</literal>.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argname</replaceable></term>

    <listitem>
     <para>
      The name of an argument.
      Note that <command>DROP AGGREGATE</command> does not actually pay
      any attention to argument names, since only the argument data
      types are needed to determine the aggregate function's identity.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argtype</replaceable></term>
    <listitem>
     <para>
      An input data type on which the aggregate function operates.
      To reference a zero-argument aggregate function, write <literal>*</literal>
      in place of the list of argument specifications.
      To reference an ordered-set aggregate function, write
      <literal>ORDER BY</literal> between the direct and aggregated argument
      specifications.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CASCADE</literal></term>
    <listitem>
     <para>
      Automatically drop objects that depend on the aggregate function
      (such as views using it),
      and in turn all objects that depend on those objects
      (see <xref linkend="ddl-depend"/>).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RESTRICT</literal></term>
    <listitem>
     <para>
      Refuse to drop the aggregate function if any objects depend on
      it.  This is the default.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

   <para>
    Alternative syntaxes for referencing ordered-set aggregates
    are described under <xref linkend="sql-alteraggregate"/>.
   </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   To remove the aggregate function <literal>myavg</literal> for type
   <type>integer</type>:
<programlisting>
DROP AGGREGATE myavg(integer);
</programlisting>
  </para>

  <para>
   To remove the hypothetical-set aggregate function <literal>myrank</literal>,
   which takes an arbitrary list of ordering columns and a matching list
   of direct arguments:
<programlisting>
DROP AGGREGATE myrank(VARIADIC "any" ORDER BY VARIADIC "any");
</programlisting>
  </para>

  <para>
   To remove multiple aggregate functions in one command:
<programlisting>
DROP AGGREGATE myavg(integer), myavg(bigint);
</programlisting></para>
</refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   There is no <command>DROP AGGREGATE</command> statement in the SQL
   standard.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-alteraggregate"/></member>
   <member><xref linkend="sql-createaggregate"/></member>
  </simplelist>
 </refsect1>

</refentry>