数据库系统

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drop_table.sgml：源码内容
							<refentry id="SQL-DROPTABLE">
 <refmeta>
  <refentrytitle>
   DROP TABLE
  </refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>
 <refnamediv>
  <refname>
   DROP TABLE
  </refname>
  <refpurpose>
   Removes existing tables from a database
  </refpurpose>
 </refnamediv>
 <refsynopsisdiv>
  <refsynopsisdivinfo>
   <date>1998-09-22</date>
  </refsynopsisdivinfo>
  <synopsis>
DROP TABLE <replaceable class="PARAMETER">name</replaceable> [, ...]
  </synopsis>
  
  <refsect2 id="R2-SQL-DROPTABLE-1">
   <refsect2info>
    <date>1998-09-22</date>
   </refsect2info>
   <title>
    Inputs
   </title>
   <para>
    <variablelist>
     <varlistentry>
      <term><replaceable class="PARAMETER">name</replaceable></term>
      <listitem>
       <para>
	The name of an existing table or view to drop.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
  <refsect2 id="R2-SQL-DROPTABLE-2">
   <refsect2info>
    <date>1998-09-22</date>
   </refsect2info>
   <title>
    Outputs
   </title>
   <para>
    <variablelist>
     <varlistentry>
      <term><computeroutput>
DROP
       </computeroutput></term>
      <listitem>
       <para>
	The message returned if the command completes successfully.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term><computeroutput>
ERROR Relation "<replaceable class="parameter">name</replaceable>" Does Not Exist!
       </computeroutput></term>
      <listitem>
       <para>
	If the specified table or view does not exist in the database.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
 </refsynopsisdiv>
 
 <refsect1 id="R1-SQL-DROPTABLE-1">
  <refsect1info>
   <date>1998-09-22</date>
  </refsect1info>
  <title>
   Description
  </title>
  <para>
   <command>DROP TABLE</command> removes tables and views from the database.
   Only its owner may destroy a table or view. A table
   may be emptied of rows, but not destroyed, by using <command>DELETE</command>.
  </para>
  <para>
   If a table being destroyed has secondary indexes on it,
   they will be removed first. The removal of just a
   secondary index will not affect the contents of the underlying table.
  </para>
  <refsect2 id="R2-SQL-DROPTABLE-3">
   <refsect2info>
    <date>1998-09-22</date>
   </refsect2info>
   <title>
    Notes
   </title>
   <para>
    Refer to <command>CREATE TABLE</command> and
    <command>ALTER TABLE</command> for information on
    how to create or modify tables.
   </para>
  </refsect2>
 </refsect1>
 <refsect1 id="R1-SQL-DROPTABLE-2">
  <title>
   Usage
  </title>
  <para>
   To destroy two tables, <literal>films</literal> and 
   <command>distributors</command>:
   <programlisting>
DROP TABLE films, distributors;
   </programlisting>
  </para>
 </refsect1>
 
 <refsect1 id="R1-SQL-DROPTABLE-3">
   <title>
   Compatibility
  </title>
  <para>
  </para>
  
  <refsect2 id="R2-SQL-DROPTABLE-4">
   <refsect2info>
    <date>1998-09-22</date>
   </refsect2info>
   <title>
    SQL92
   </title>
   <para>
    SQL92 specifies some additional capabilities for DROP TABLE:
   </para>
   <synopsis>
DROP TABLE <replaceable class="parameter">table</replaceable> { RESTRICT | CASCADE }
   </synopsis>
   <variablelist>
    <varlistentry>
     <term>RESTRICT</term>
     <listitem>
      <para>
       Ensures that only a table with no dependent views or
       integrity constraints can be destroyed.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>CASCADE</term>
     <listitem>
      <para>
       Any referencing views or integrity constraints
       will also be dropped.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
    <tip>
    <para>
     At present, to remove a referenced view you must drop
     it explicitly.
    </para>
   </tip>
   </refsect2>
 </refsect1>
</refentry>
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