253 lines
6.1 KiB
Plaintext
253 lines
6.1 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_view.sgml,v 1.9 2000/03/27 17:14:42 thomas Exp $
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Postgres documentation
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-->
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<refentry id="SQL-CREATEVIEW">
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<refmeta>
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<refentrytitle id="SQL-CREATEVIEW-TITLE">
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CREATE VIEW
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</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>
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CREATE VIEW
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</refname>
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<refpurpose>
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Constructs a virtual table
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</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>2000-03-25</date>
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</refsynopsisdivinfo>
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<synopsis>
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CREATE VIEW <replaceable class="PARAMETER">view</replaceable> AS SELECT <replaceable class="PARAMETER">query</replaceable>
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</synopsis>
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<refsect2 id="R2-SQL-CREATEVIEW-1">
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<refsect2info>
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<date>2000-03-25</date>
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</refsect2info>
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<title>
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Inputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><replaceable class="parameter">view</replaceable></term>
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<listitem>
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<para>
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The name of a view 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 class="parameter">query</replaceable></term>
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<listitem>
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<para>
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An SQL query which will provide the columns and rows of the view.
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</para>
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<para>
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Refer to the SELECT statement for more information
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about valid arguments.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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<refsect2 id="R2-SQL-CREATEVIEW-2">
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<refsect2info>
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<date>2000-03-25</date>
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</refsect2info>
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<title>
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Outputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><computeroutput>
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CREATE
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</computeroutput></term>
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<listitem>
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<para>
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The message returned if the view is successfully 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><computeroutput>
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ERROR: Relation '<replaceable class="parameter">view</replaceable>' already exists
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</computeroutput></term>
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<listitem>
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<para>
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This error occurs if the view specified already exists in the database.
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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><computeroutput>
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NOTICE create: attribute named "<replaceable class="parameter">column</replaceable>" has an unknown type
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</computeroutput></term>
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<listitem>
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<para>
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The view will be created having a column with an unknown type
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if you do not specify it. For example, the following command gives
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a warning:
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<programlisting>
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CREATE VIEW vista AS SELECT 'Hello World'
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</programlisting>
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whereas this command does not:
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<programlisting>
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CREATE VIEW vista AS SELECT text 'Hello World'
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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</refsynopsisdiv>
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<refsect1 id="R1-SQL-CREATEVIEW-1">
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<refsect1info>
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<date>2000-03-25</date>
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</refsect1info>
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<title>
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Description
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</title>
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<para>
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<command>CREATE VIEW</command> will define a view of a table or
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class. This view is not physically materialized. Specifically, a query
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rewrite retrieve rule is automatically generated to support
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retrieve operations on views.
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</para>
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<refsect2 id="R2-SQL-CREATEVIEW-3">
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<refsect2info>
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<date>2000-03-25</date>
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</refsect2info>
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<title>
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Notes
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</title>
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<para>
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Currently, views are read only.
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</para>
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<para>
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Use the <command>DROP VIEW</command> statement to drop views.
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</para>
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</refsect2>
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</refsect1>
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<refsect1 id="R1-SQL-CREATEVIEW-2">
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<title>
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Usage
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</title>
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<para>
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Create a view consisting of all Comedy films:
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<programlisting>
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CREATE VIEW kinds AS
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SELECT *
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FROM films
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WHERE kind = 'Comedy';
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SELECT * FROM kinds;
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code | title | did | date_prod | kind | len
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-------+---------------------------+-----+------------+--------+-------
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UA502 | Bananas | 105 | 1971-07-13 | Comedy | 01:22
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C_701 | There's a Girl in my Soup | 107 | 1970-06-11 | Comedy | 01:36
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(2 rows)
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-CREATEVIEW-3">
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<title>
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Compatibility
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</title>
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<refsect2 id="R2-SQL-CREATEVIEW-5">
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<refsect2info>
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<date>2000-03-25</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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SQL92 specifies some additional capabilities for the
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<command>CREATE VIEW</command> statement:
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</para>
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<synopsis>
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CREATE VIEW <replaceable class="parameter">view</replaceable> [ <replaceable class="parameter">column</replaceable> [, ...] ]
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AS SELECT <replaceable class="parameter">expression</replaceable> [ AS <replaceable class="parameter">colname</replaceable> ] [, ...]
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FROM <replaceable class="parameter">table</replaceable> [ WHERE <replaceable class="parameter">condition</replaceable> ]
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[ WITH [ CASCADE | LOCAL ] CHECK OPTION ]
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</synopsis>
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<para>
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The optional clauses for the full SQL92 command are:
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<variablelist>
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<varlistentry>
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<term>CHECK OPTION</term>
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<listitem>
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<para>
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This option is to do with updatable views.
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All INSERTs and UPDATEs on the view will be
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checked to ensure data satisfy the view-defining
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condition. If they do not, the update will be rejected.
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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>LOCAL</term>
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<listitem>
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<para>
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Check for integrity on this view.
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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>CASCADE</term>
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<listitem>
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<para>
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Check for integrity on this view and on any dependent
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view. CASCADE is assumed if neither CASCADE nor LOCAL is specified.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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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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