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Add BY clause to PL/PgSQL FOR loop, to control the iteration increment.

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Jaime Casanova
This commit is contained in:
Bruce Momjian
2006-06-12 16:45:30 +00:00
parent e6a7b01930
commit 07c25723da
6 changed files with 73 additions and 13 deletions
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15
doc/src/sgml/plpgsql.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.94 2006/05/30 13:40:55 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.95 2006/06/12 16:45:30 momjian Exp $ -->
<chapter id="plpgsql">
<title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@ -1975,7 +1975,7 @@ END LOOP;
<synopsis>
<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
FOR <replaceable>name</replaceable> IN <optional> REVERSE </optional> <replaceable>expression</replaceable> .. <replaceable>expression</replaceable> LOOP
FOR <replaceable>name</replaceable> IN <optional> REVERSE </optional> <replaceable>expression</replaceable> .. <replaceable>expression</replaceable> <optional> BY <replaceable>expression</replaceable> </optional> LOOP
<replaceable>statements</replaceable>
END LOOP <optional> <replaceable>label</replaceable> </optional>;
</synopsis>
@ -1988,8 +1988,10 @@ END LOOP <optional> <replaceable>label</replaceable> </optional>;
definition of the variable name is ignored within the loop).
The two expressions giving
the lower and upper bound of the range are evaluated once when entering
the loop. The iteration step is normally 1, but is -1 when <literal>REVERSE</> is
specified.
the loop. If the <literal>BY</> clause isn't specified the iteration
step is 1 otherwise it's the value specified in the <literal>BY</>
clause. If <literal>REVERSE</> is specified then the step value is
considered negative.
</para>
<para>
@ -2003,6 +2005,11 @@ END LOOP;
FOR i IN REVERSE 10..1 LOOP
-- some computations here
END LOOP;
FOR i IN REVERSE 10..1 BY 2 LOOP
-- some computations here
RAISE NOTICE 'i is %', i;
END LOOP;
</programlisting>
</para>