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Add support for an optional INTO clause to PL/PgSQL's EXECUTE command.
This allows the result of executing a SELECT to be assigned to a row variable, record variable, or list of scalars. Docs and regression tests updated. Per Pavel Stehule, improvements and cleanup by Neil Conway.
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.69 2005/05/26 04:08:31 momjian Exp $
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$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.70 2005/06/07 02:47:15 neilc Exp $
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-->
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<chapter id="plpgsql">
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@ -1251,13 +1251,14 @@ NULL;
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<command>EXECUTE</command> statement is provided:
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<synopsis>
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EXECUTE <replaceable class="command">command-string</replaceable>;
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EXECUTE <replaceable class="command">command-string</replaceable> [ INTO <replaceable>target</replaceable> ];
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</synopsis>
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where <replaceable>command-string</replaceable> is an expression
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yielding a string (of type
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<type>text</type>) containing the command
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to be executed. This string is fed literally to the SQL engine.
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yielding a string (of type <type>text</type>) containing the
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command to be executed and <replaceable>target</replaceable> is a
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record variable, row variable, or a comma-separated list of
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simple variables and record/row fields.
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</para>
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<para>
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@ -1276,16 +1277,22 @@ EXECUTE <replaceable class="command">command-string</replaceable>;
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</para>
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<para>
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The results from <command>SELECT</command> commands are discarded
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by <command>EXECUTE</command>, and <command>SELECT INTO</command>
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is not currently supported within <command>EXECUTE</command>.
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So there is no way to extract a result from a dynamically-created
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<command>SELECT</command> using the plain <command>EXECUTE</command>
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command. There are two other ways to do it, however: one is to use the
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<command>FOR-IN-EXECUTE</>
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loop form described in <xref linkend="plpgsql-records-iterating">,
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and the other is to use a cursor with <command>OPEN-FOR-EXECUTE</>, as
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described in <xref linkend="plpgsql-cursor-opening">.
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The <literal>INTO</literal> clause specifies where the results of
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a <command>SELECT</command> command should be assigned. If a row
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or variable list is provided, it must exactly match the structure
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of the results produced by the <command>SELECT</command> (when a
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record variable is used, it will configure itself to match the
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result's structure automatically). If multiple rows are returned,
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only the first will be assigned to the <literal>INTO</literal>
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variable. If no rows are returned, NULL is assigned to the
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<literal>INTO</literal> variable. If no <literal>INTO</literal>
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clause is specified, the results of a <command>SELECT</command>
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command are discarded.
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</para>
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<para>
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<command>SELECT INTO</command> is not currently supported within
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<command>EXECUTE</command>.
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</para>
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<para>
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@ -1364,7 +1371,7 @@ EXECUTE 'UPDATE tbl SET '
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command, which has the form:
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<synopsis>
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GET DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional> ;
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GET DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional>;
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</synopsis>
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This command allows retrieval of system status indicators. Each
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@ -2173,7 +2180,7 @@ SELECT merge_db (1, 'dennis');
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Another way is to use the cursor declaration syntax,
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which in general is:
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<synopsis>
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<replaceable>name</replaceable> CURSOR <optional> ( <replaceable>arguments</replaceable> ) </optional> FOR <replaceable>query</replaceable> ;
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<replaceable>name</replaceable> CURSOR <optional> ( <replaceable>arguments</replaceable> ) </optional> FOR <replaceable>query</replaceable>;
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</synopsis>
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(<literal>FOR</> may be replaced by <literal>IS</> for
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<productname>Oracle</productname> compatibility.)
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@ -2218,7 +2225,7 @@ DECLARE
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<title><command>OPEN FOR</command> <replaceable>query</replaceable></title>
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<synopsis>
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OPEN <replaceable>unbound_cursor</replaceable> FOR <replaceable>query</replaceable> ;
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OPEN <replaceable>unbound_cursor</replaceable> FOR <replaceable>query</replaceable>;
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</synopsis>
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<para>
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@ -3188,7 +3195,7 @@ DECLARE
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func_body text;
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func_cmd text;
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BEGIN
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func_body := 'BEGIN' ;
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func_body := 'BEGIN';
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-- Notice how we scan through the results of a query in a FOR loop
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-- using the FOR <record> construct.
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