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IDs in SGML are case insensitive, and we have accumulated a mix of upper and lower case IDs, including different variants of the same ID. In XML, these will be case sensitive, so we need to fix up those differences. Going to all lower case seems most straightforward, and the current build process already makes all anchors and lower case anyway during the SGML->XML conversion, so this doesn't create any difference in the output right now. A future XML-only build process would, however, maintain any mixed case ID spellings in the output, so that is another reason to clean this up beforehand. Author: Alexander Lakhin <exclusion@gmail.com>
356 lines
11 KiB
Plaintext
356 lines
11 KiB
Plaintext
<!--
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doc/src/sgml/ref/create_table_as.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-createtableas">
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<indexterm zone="sql-createtableas">
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<primary>CREATE TABLE AS</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>CREATE TABLE AS</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>CREATE TABLE AS</refname>
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<refpurpose>define a new table from the results of a query</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <replaceable>table_name</replaceable>
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[ (<replaceable>column_name</replaceable> [, ...] ) ]
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[ WITH ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
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[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
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[ TABLESPACE <replaceable class="parameter">tablespace_name</replaceable> ]
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AS <replaceable>query</replaceable>
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[ WITH [ NO ] DATA ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>CREATE TABLE AS</command> creates a table and fills it
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with data computed by a <command>SELECT</command> command.
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The table columns have the
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names and data types associated with the output columns of the
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<command>SELECT</command> (except that you can override the column
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names by giving an explicit list of new column names).
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</para>
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<para>
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<command>CREATE TABLE AS</command> bears some resemblance to
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creating a view, but it is really quite different: it creates a new
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table and evaluates the query just once to fill the new table
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initially. The new table will not track subsequent changes to the
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source tables of the query. In contrast, a view re-evaluates its
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defining <command>SELECT</command> statement whenever it is
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queried.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><literal>GLOBAL</literal> or <literal>LOCAL</literal></term>
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<listitem>
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<para>
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Ignored for compatibility. Use of these keywords is deprecated;
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refer to <xref linkend="sql-createtable"> for details.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist>
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<varlistentry>
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<term><literal>TEMPORARY</literal> or <literal>TEMP</literal></term>
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<listitem>
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<para>
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If specified, the table is created as a temporary table.
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Refer to <xref linkend="sql-createtable"> for details.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>UNLOGGED</literal></term>
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<listitem>
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<para>
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If specified, the table is created as an unlogged table.
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Refer to <xref linkend="sql-createtable"> for details.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>IF NOT EXISTS</literal></term>
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<listitem>
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<para>
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Do not throw an error if a relation with the same name already exists.
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A notice is issued in this case. Refer to <xref linkend="sql-createtable">
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for details.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>table_name</replaceable></term>
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<listitem>
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<para>
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The name (optionally schema-qualified) of the table to be created.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>column_name</replaceable></term>
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<listitem>
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<para>
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The name of a column in the new table. If column names are not
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provided, they are taken from the output column names of the query.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>WITH ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )</literal></term>
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<listitem>
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<para>
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This clause specifies optional storage parameters for the new table;
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see <xref linkend="sql-createtable-storage-parameters"
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endterm="sql-createtable-storage-parameters-title"> for more
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information. The <literal>WITH</literal> clause
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can also include <literal>OIDS=TRUE</literal> (or just <literal>OIDS</literal>)
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to specify that rows of the new table
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should have OIDs (object identifiers) assigned to them, or
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<literal>OIDS=FALSE</literal> to specify that the rows should not have OIDs.
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See <xref linkend="sql-createtable"> for more information.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>WITH OIDS</literal></term>
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<term><literal>WITHOUT OIDS</literal></term>
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<listitem>
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<para>
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These are obsolescent syntaxes equivalent to <literal>WITH (OIDS)</literal>
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and <literal>WITH (OIDS=FALSE)</literal>, respectively. If you wish to give
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both an <literal>OIDS</literal> setting and storage parameters, you must use
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the <literal>WITH ( ... )</literal> syntax; see above.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ON COMMIT</literal></term>
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<listitem>
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<para>
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The behavior of temporary tables at the end of a transaction
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block can be controlled using <literal>ON COMMIT</literal>.
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The three options are:
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<variablelist>
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<varlistentry>
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<term><literal>PRESERVE ROWS</literal></term>
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<listitem>
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<para>
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No special action is taken at the ends of transactions.
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This is the default behavior.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>DELETE ROWS</literal></term>
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<listitem>
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<para>
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All rows in the temporary table will be deleted at the end
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of each transaction block. Essentially, an automatic <xref
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linkend="sql-truncate"> is done
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at each commit.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>DROP</literal></term>
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<listitem>
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<para>
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The temporary table will be dropped at the end of the current
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transaction block.
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</para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>TABLESPACE <replaceable class="parameter">tablespace_name</replaceable></literal></term>
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<listitem>
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<para>
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The <replaceable class="parameter">tablespace_name</replaceable> is the name
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of the tablespace in which the new table is to be created.
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If not specified,
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<xref linkend="guc-default-tablespace"> is consulted, or
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<xref linkend="guc-temp-tablespaces"> if the table is temporary.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>query</replaceable></term>
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<listitem>
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<para>
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A <xref linkend="sql-select">, <link
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linkend="sql-table">TABLE</link>, or <xref linkend="sql-values">
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command, or an <xref linkend="sql-execute"> command that runs a
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prepared <command>SELECT</command>, <command>TABLE</command>, or
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<command>VALUES</command> query.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>WITH [ NO ] DATA</literal></term>
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<listitem>
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<para>
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This clause specifies whether or not the data produced by the query
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should be copied into the new table. If not, only the table structure
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is copied. The default is to copy the data.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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This command is functionally similar to <xref
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linkend="sql-selectinto">, but it is
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preferred since it is less likely to be confused with other uses of
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the <command>SELECT INTO</command> syntax. Furthermore, <command>CREATE
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TABLE AS</command> offers a superset of the functionality offered
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by <command>SELECT INTO</command>.
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</para>
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<para>
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The <command>CREATE TABLE AS</command> command allows the user to
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explicitly specify whether OIDs should be included. If the
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presence of OIDs is not explicitly specified,
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the <xref linkend="guc-default-with-oids"> configuration variable is
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used.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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Create a new table <literal>films_recent</literal> consisting of only
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recent entries from the table <literal>films</literal>:
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<programlisting>
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CREATE TABLE films_recent AS
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SELECT * FROM films WHERE date_prod >= '2002-01-01';
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</programlisting>
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</para>
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<para>
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To copy a table completely, the short form using
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the <literal>TABLE</literal> command can also be used:
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<programlisting>
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CREATE TABLE films2 AS
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TABLE films;
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</programlisting>
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</para>
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<para>
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Create a new temporary table <literal>films_recent</literal>, consisting of
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only recent entries from the table <literal>films</literal>, using a
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prepared statement. The new table has OIDs and will be dropped at commit:
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<programlisting>
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PREPARE recentfilms(date) AS
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SELECT * FROM films WHERE date_prod > $1;
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CREATE TEMP TABLE films_recent WITH (OIDS) ON COMMIT DROP AS
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EXECUTE recentfilms('2002-01-01');
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</programlisting></para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>CREATE TABLE AS</command> conforms to the <acronym>SQL</acronym>
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standard. The following are nonstandard extensions:
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<itemizedlist spacing="compact">
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<listitem>
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<para>
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The standard requires parentheses around the subquery clause; in
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<productname>PostgreSQL</productname>, these parentheses are
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optional.
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</para>
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</listitem>
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<listitem>
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<para>
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In the standard, the <literal>WITH [ NO ] DATA</literal> clause
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is required; in PostgreSQL it is optional.
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</para>
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</listitem>
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<listitem>
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<para><productname>PostgreSQL</productname> handles temporary tables in a way
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rather different from the standard; see
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<xref linkend="sql-createtable">
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for details.
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</para>
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</listitem>
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<listitem>
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<para>
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The <literal>WITH</literal> clause is a <productname>PostgreSQL</productname>
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extension; neither storage parameters nor OIDs are in the standard.
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</para>
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</listitem>
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<listitem>
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<para>
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The <productname>PostgreSQL</productname> concept of tablespaces is not
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part of the standard. Hence, the clause <literal>TABLESPACE</literal>
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is an extension.
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</para>
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</listitem>
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</itemizedlist></para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-creatematerializedview"></member>
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<member><xref linkend="sql-createtable"></member>
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<member><xref linkend="sql-execute"></member>
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<member><xref linkend="sql-select"></member>
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<member><xref linkend="sql-selectinto"></member>
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<member><xref linkend="sql-values"></member>
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</simplelist>
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</refsect1>
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</refentry>
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