229 lines
7.3 KiB
Plaintext
229 lines
7.3 KiB
Plaintext
<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.24 2004/09/23 03:43:57 neilc Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-CREATETABLEAS">
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<refmeta>
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<refentrytitle id="sql-createtableas-title">CREATE TABLE AS</refentrytitle>
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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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<indexterm zone="sql-createtableas">
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<primary>CREATE TABLE AS</primary>
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</indexterm>
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<refsynopsisdiv>
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<synopsis>
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CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable>table_name</replaceable> [ (<replaceable>column_name</replaceable> [, ...] ) ] [ [ WITH | WITHOUT ] OIDS ]
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AS <replaceable>query</replaceable>
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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 or an
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<command>EXECUTE</command> that runs a prepared
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<command>SELECT</command> command. 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. Refer to <xref
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linkend="sql-createtable" endterm="sql-createtable-title"> for
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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</> or <literal>TEMP</></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" endterm="sql-createtable-title"> 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
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query. If the table is created out of an
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<command>EXECUTE</command> command, a column name list can
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currently not be specified.
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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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This optional clause specifies whether the table created by
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<command>CREATE TABLE AS</command> should include OIDs. If
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neither form of this clause if specified, the value of the
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<xref linkend="guc-default-with-oids"> configuration parameter is
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used.
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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 query statement (that is, a <command>SELECT</command> command
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or an <command>EXECUTE</command> command that runs a prepared
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<command>SELECT</command> command). Refer to <xref
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linkend="sql-select" endterm="sql-select-title"> or <xref
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linkend="sql-execute" endterm="sql-execute-title">,
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respectively, for a description of the allowed syntax.
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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" endterm="sql-selectinto-title">, 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</> syntax. Furthermore, <command>CREATE
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TABLE AS</command> offers a superset of the functionality offerred
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by <command>SELECT INTO</command>.
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</para>
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<para>
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Prior to <productname>PostgreSQL</productname> 8.0, <command>CREATE
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TABLE AS</command> always included OIDs in the table it
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produced. Furthermore, these OIDs were newly generated: they were
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distinct from the OIDs of any of the rows in the source tables of
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the <command>SELECT</command> or <command>EXECUTE</command>
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statement. Therefore, if <command>CREATE TABLE AS</command> was
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frequently executed, the OID counter would be rapidly
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incremented. As of <productname>PostgresSQL</productname> 8.0,
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the <command>CREATE TABLE AS</command> command allows the user to
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explicitely specify whether OIDs should be included. If the
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presence of OIDs is not explicitely specified,
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the <xref linkend="guc-default-with-oids"> configuration variable is
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used. While this variable currently defaults to true, the default
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value may be changed in the future. Therefore, applications that
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require OIDs in the table created by <command>CREATE TABLE
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AS</command> should explicitely specify <literal>WITH
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OIDS</literal> to ensure compatibility with future versions
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of <productname>PostgreSQL</productname>.
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</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> is specified by the SQL2003
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standard. There are some small differences between the definition
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of the command in SQL2003 and its implementation in
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<productname>PostgreSQL</>:
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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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The standard defines an <literal>ON COMMIT</literal> clause;
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this is not currently implemented by <productname>PostgreSQL</>.
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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 standard defines a <literal>WITH DATA</literal> clause;
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this is not currently implemented by <productname>PostgreSQL</>.
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</para>
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</listitem>
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</itemizedlist>
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</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-createtable" endterm="sql-createtable-title"></member>
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<member><xref linkend="sql-execute" endterm="sql-execute-title"></member>
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<member><xref linkend="sql-select" endterm="sql-select-title"></member>
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<member><xref linkend="sql-selectinto" endterm="sql-selectinto-title"></member>
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</simplelist>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:nil
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:"/usr/lib/sgml/catalog"
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sgml-local-ecat-files:nil
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End:
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-->
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