drop_type.sgml

来自「postgresql8.3.4源码,开源数据库」· SGML 代码 · 共 115 行

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$PostgreSQL: pgsql/doc/src/sgml/ref/drop_type.sgml,v 1.30 2007/05/15 19:13:55 neilc Exp $
PostgreSQL documentation
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<refentry id="SQL-DROPTYPE">
 <refmeta>
  <refentrytitle id="SQL-DROPTYPE-TITLE">DROP TYPE</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>DROP TYPE</refname>
  <refpurpose>remove a data type</refpurpose>
 </refnamediv>

 <indexterm zone="sql-droptype">
  <primary>DROP TYPE</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
DROP TYPE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>DROP TYPE</command> removes a user-defined data type.
   Only the owner of a type can remove it.
  </para>
 </refsect1>
  
 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><literal>IF EXISTS</literal></term>
    <listitem>
     <para>
      Do not throw an error if the type 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 the data type to remove.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CASCADE</literal></term>
    <listitem>
     <para>
      Automatically drop objects that depend on the type (such as
      table columns, functions, operators).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RESTRICT</literal></term>
    <listitem>
     <para>
      Refuse to drop the type if any objects depend on it.  This is
      the default.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>
  
 <refsect1 id="SQL-DROPTYPE-examples">
  <title>Examples</title>

  <para>
   To remove the data type <type>box</type>:
<programlisting>
DROP TYPE box;
</programlisting>
  </para>
 </refsect1>

 <refsect1 id="SQL-DROPTYPE-compatibility">
  <title>Compatibility</title>

  <para>
   This command is similar to the corresponding command in the SQL
   standard, apart from the <literal>IF EXISTS</>
   option, which is a <productname>PostgreSQL</> extension.
   But note that the <command>CREATE TYPE</command> command
   and the data type extension mechanisms in
   <productname>PostgreSQL</productname> differ from the SQL standard.
  </para>
 </refsect1>

 <refsect1 id="SQL-DROPTYPE-see-also">
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-createtype" endterm="sql-createtype-title"></member>
   <member><xref linkend="sql-altertype" endterm="sql-altertype-title"></member>
  </simplelist>
 </refsect1>

</refentry>