postgresql/doc/src/sgml/ref/create_table_as.sgml

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$PostgreSQL: pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.23 2004/08/24 00:06:51 neilc Exp $
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<refentry id="SQL-CREATETABLEAS">
 <refmeta>
  <refentrytitle id="sql-createtableas-title">CREATE TABLE AS</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>CREATE TABLE AS</refname>
  <refpurpose>define a new table from the results of a query</refpurpose>
 </refnamediv>

 <indexterm zone="sql-createtableas">
  <primary>CREATE TABLE AS</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable>table_name</replaceable> [ (<replaceable>column_name</replaceable> [, ...] ) ] [ [ WITH | WITHOUT ] OIDS ]
    AS <replaceable>query</replaceable>
</synopsis>
 </refsynopsisdiv>
  
 <refsect1>
  <title>Description</title>

  <para>
   <command>CREATE TABLE AS</command> creates a table and fills it
   with data computed by a <command>SELECT</command> command or an
   <command>EXECUTE</command> that runs a prepared
   <command>SELECT</command> command.  The table columns have the
   names and data types associated with the output columns of the
   <command>SELECT</command> (except that you can override the column
   names by giving an explicit list of new column names).
  </para>

  <para>
   <command>CREATE TABLE AS</command> bears some resemblance to
   creating a view, but it is really quite different: it creates a new
   table and evaluates the query just once to fill the new table
   initially.  The new table will not track subsequent changes to the
   source tables of the query.  In contrast, a view re-evaluates its
   defining <command>SELECT</command> statement whenever it is
   queried.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><literal>GLOBAL</literal> or <literal>LOCAL</literal></term>
    <listitem>
     <para>
      Ignored for compatibility. Refer to <xref
      linkend="sql-createtable" endterm="sql-createtable-title"> for
      details.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <variablelist>
   <varlistentry>
    <term><literal>TEMPORARY</> or <literal>TEMP</></term>
    <listitem>
     <para>
      If specified, the table is created as a temporary table.
      Refer to <xref linkend="sql-createtable" endterm="sql-createtable-title"> for details.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable>table_name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of the table to be created.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable>column_name</replaceable></term>
    <listitem>
     <para>
      The name of a column in the new table.  If column names are not
      provided, they are taken from the output column names of the
      query.  If the table is created out of an
      <command>EXECUTE</command> command, a column name list can
      currently not be specified.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>WITH OIDS</literal></term>
    <term><literal>WITHOUT OIDS</literal></term>
     <listitem>
      <para>
       This optional clause specifies whether the table created by
       <command>CREATE TABLE AS</command> should include OIDs. If
       neither form of this clause if specified, the value of the
       <xref linkend="guc-default-with-oids"> configuration parameter is
       used.
      </para>
     </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable>query</replaceable></term>
    <listitem>
     <para>
      A query statement (that is, a <command>SELECT</command> command
      or an <command>EXECUTE</command> command that runs a prepared
      <command>SELECT</command> command).  Refer to <xref
      linkend="sql-select" endterm="sql-select-title"> or <xref
      linkend="sql-execute" endterm="sql-execute-title">,
      respectively, for a description of the allowed syntax.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   This command is functionally similar to <xref
   linkend="sql-selectinto" endterm="sql-selectinto-title">, but it is
   preferred since it is less likely to be confused with other uses of
   the <command>SELECT INTO</> syntax. Furthermore, <command>CREATE
   TABLE AS</command> offers a superset of the functionality offerred
   by <command>SELECT INTO</command>.
  </para>

  <para>
   Prior to <productname>PostgreSQL</productname> 8.0, <command>CREATE
   TABLE AS</command> always included OIDs in the table it
   produced. Furthermore, these OIDs were newly generated: they were
   distinct from the OIDs of any of the rows in the source tables of
   the <command>SELECT</command> or <command>EXECUTE</command>
   statement. Therefore, if <command>CREATE TABLE AS</command> was
   frequently executed, the OID counter would be rapidly
   incremented. As of <productname>PostgresSQL</productname> 8.0,
   the <command>CREATE TABLE AS</command> command allows the user to
   explicitely specify whether OIDs should be included. If the
   presence of OIDs is not explicitely specified,
   the <xref linkend="guc-default-with-oids"> configuration variable is
   used. While this variable currently defaults to true, the default
   value may be changed in the future. Therefore, applications that
   require OIDs in the table created by <command>CREATE TABLE
   AS</command> should explicitely specify <literal>WITH
   OIDS</literal> to ensure compatibility with future versions
   of <productname>PostgreSQL</productname>.
  </para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   This command is modeled after an <productname>Oracle</productname>
   feature.  There is no command with equivalent functionality in
   the SQL standard.  However, a combination of <literal>CREATE
   TABLE</literal> and <literal>INSERT ... SELECT</literal> can
   accomplish the same thing with little more effort.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createtable" endterm="sql-createtable-title"></member>
   <member><xref linkend="sql-execute" endterm="sql-execute-title"></member>
   <member><xref linkend="sql-select" endterm="sql-select-title"></member>
   <member><xref linkend="sql-selectinto" endterm="sql-selectinto-title"></member>
  </simplelist>
 </refsect1>
 
</refentry>

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