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$PostgreSQL: pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.36 2006/09/18 19:54:01 tgl 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 table_name
   [(column_name [, ...] )]
   [ WITH ( storage_parameter=value [, ... ] )
   [ON COMMIT {PRESERVE ROWS | DELETE ROWS | DROP}]
   [TABLESPACE tablespace]
   AS query
   [DISTRIBUTED BY (column, [ ... ] ) | DISTRIBUTED RANDOMLY]

where storage_parameter is:

   APPENDONLY={TRUE|FALSE}
   BLOCKSIZE={8192-2097152}
   ORIENTATION={PARQUET|ROW}
   COMPRESSTYPE={ZLIB|SNAPPY|GZIP|NONE}
   COMPRESSLEVEL={0-9}
   FILLFACTOR={10-100}
   OIDS[=TRUE|FALSE]


</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.

   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 from an

      <command>EXECUTE</command> command, a column name list cannot be

      specified.

     </para>

    </listitem>

   </varlistentry>


   <varlistentry>

    <term><literal>WITH ( <replaceable class="PARAMETER">storage_parameter</replaceable> [= <replaceable class="PARAMETER">value</replaceable>] [, ... ] )</literal></term>

    <listitem>

     <para>

      This clause specifies optional storage parameters for the new table;

      see <xref linkend="sql-createtable-storage-parameters"

      endterm="sql-createtable-storage-parameters-title"> for more

      information.  The <literal>WITH</> clause

      can also include <literal>OIDS=TRUE</> (or just <literal>OIDS</>)

      to specify that rows of the new table

      should have OIDs (object identifiers) assigned to them, or

      <literal>OIDS=FALSE</> to specify that the rows should not have OIDs.

      See <xref linkend="sql-createtable"

      endterm="sql-createtable-title"> for more information.

     </para>

    </listitem>

   </varlistentry>


   <varlistentry>

    <term><literal>WITH OIDS</></term>

    <term><literal>WITHOUT OIDS</></term>

    <listitem>

     <para>

      These are obsolescent syntaxes equivalent to <literal>WITH (OIDS)</>

      and <literal>WITH (OIDS=FALSE)</>, respectively.  If you wish to give

      both an <literal>OIDS</> setting and storage parameters, you must use

      the <literal>WITH ( ... )</> syntax; see above.

     </para>

    </listitem>

   </varlistentry>


   <varlistentry>

    <term><literal>ON COMMIT</literal></term>

    <listitem>

     <para>

      The behavior of temporary tables at the end of a transaction

      block can be controlled using <literal>ON COMMIT</literal>.

      The three options are:


      <variablelist>

       <varlistentry>

        <term><literal>PRESERVE ROWS</literal></term>

        <listitem>

         <para>

          No special action is taken at the ends of transactions.

          This is the default behavior.

         </para>

        </listitem>

       </varlistentry>


       <varlistentry>

        <term><literal>DELETE ROWS</literal></term>

        <listitem>

         <para>

          All rows in the temporary table will be deleted at the end

          of each transaction block.  Essentially, an automatic <xref

          linkend="sql-truncate" endterm="sql-truncate-title"> is done

          at each commit.

         </para>

        </listitem>

       </varlistentry>


       <varlistentry>

        <term><literal>DROP</literal></term>

        <listitem>

         <para>

          The temporary table will be dropped at the end of the current

          transaction block.

         </para>

        </listitem>

       </varlistentry>

      </variablelist>

     </para>

    </listitem>

   </varlistentry>


   <varlistentry>

    <term><literal>TABLESPACE <replaceable class="PARAMETER">tablespace</replaceable></literal></term>

    <listitem>

     <para>

      The <replaceable class="PARAMETER">tablespace</replaceable> is the name

      of the tablespace in which the new table is to be created.

      If not specified,

      <xref linkend="guc-default-tablespace"> is used, or the database's

      default tablespace if <varname>default_tablespace</> is an empty

      string.

     </para>

    </listitem>

   </varlistentry>


   <varlistentry>

    <term><replaceable>query</replaceable></term>

    <listitem>

     <para>

      A <xref linkend="sql-select" endterm="sql-select-title"> or

      <xref linkend="sql-values" endterm="sql-values-title"> command,

      or an <xref linkend="sql-execute" endterm="sql-execute-title"> command

      that runs a prepared <command>SELECT</> or <command>VALUES</> query.

     </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 offered

   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

   created.  As of <productname>PostgreSQL</productname> 8.0,

   the <command>CREATE TABLE AS</command> command allows the user to

   explicitly specify whether OIDs should be included. If the

   presence of OIDs is not explicitly specified,

   the <xref linkend="guc-default-with-oids"> configuration variable is

   used.  As of <productname>PostgreSQL</productname> 8.1,

   this variable is false by default, so the default behavior is not

   identical to pre-8.0 releases.  Applications that

   require OIDs in the table created by <command>CREATE TABLE

   AS</command> should explicitly specify <literal>WITH (OIDS)</literal>

   to ensure proper behavior.

  </para>

 </refsect1>


 <refsect1>

  <title>Examples</title>


  <para>

   Create a new table <literal>films_recent</literal> consisting of only

   recent entries from the table <literal>films</literal>:


<programlisting>

CREATE TABLE films_recent AS

  SELECT * FROM films WHERE date_prod &gt;= '2002-01-01';

</programlisting>

  </para>


  <para>

   Create a new temporary table <literal>films_recent</literal>, consisting of

   only recent entries from the table <literal>films</literal>, using a

   prepared statement.  The new table has OIDs and will be dropped at commit:


<programlisting>

PREPARE recentfilms(date) AS

  SELECT * FROM films WHERE date_prod &gt; $1;

CREATE TEMP TABLE films_recent WITH (OIDS) ON COMMIT DROP AS

  EXECUTE recentfilms('2002-01-01');

</programlisting>

  </para>

 </refsect1>


 <refsect1>

  <title>Compatibility</title>


  <para>

   <command>CREATE TABLE AS</command> conforms to the <acronym>SQL</acronym>

   standard, with the following exceptions:


   <itemizedlist spacing="compact">

    <listitem>

     <para>

      The standard requires parentheses around the subquery clause; in

      <productname>PostgreSQL</productname>, these parentheses are

      optional.

     </para>

    </listitem>


    <listitem>

     <para>

      The standard defines a <literal>WITH [ NO ] DATA</literal> clause;

      this is not currently implemented by <productname>PostgreSQL</>.

      The behavior provided by <productname>PostgreSQL</> is equivalent

      to the standard's <literal>WITH DATA</literal> case.

      <literal>WITH NO DATA</literal> can be simulated by appending

      <literal>LIMIT 0</> to the query.

     </para>

    </listitem>


    <listitem>

     <para>

      <productname>PostgreSQL</> handles temporary tables in a way

      rather different from the standard; see

      <xref linkend="sql-createtable" endterm="sql-createtable-title">

      for details.

     </para>

    </listitem>


    <listitem>

     <para>

      The <literal>WITH</> clause is a <productname>PostgreSQL</productname>

      extension; neither storage parameters nor OIDs are in the standard.

     </para>

    </listitem>


    <listitem>

     <para>

      The <productname>PostgreSQL</productname> concept of tablespaces is not

      part of the standard.  Hence, the clause <literal>TABLESPACE</literal>

      is an extension.

     </para>

    </listitem>

   </itemizedlist>

  </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>

   <member><xref linkend="sql-values" endterm="sql-values-title"></member>

  </simplelist>

 </refsect1>

 
</refentry>