diff options
| -rw-r--r-- | doc/src/sgml/plpgsql.sgml | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml index 562dfad728e..59ec377ea9d 100644 --- a/doc/src/sgml/plpgsql.sgml +++ b/doc/src/sgml/plpgsql.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.113 2007/07/14 23:02:25 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.114 2007/07/15 00:45:16 tgl Exp $ --> <chapter id="plpgsql"> <title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title> @@ -1757,7 +1757,7 @@ END LOOP; </para> </sect3> - <sect3> + <sect3 id="plpgsql-integer-for"> <title><literal>FOR</> (integer variant)</title> <synopsis> @@ -1777,7 +1777,8 @@ END LOOP <optional> <replaceable>label</replaceable> </optional>; the lower and upper bound of the range are evaluated once when entering 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 + clause, which again is evaluated once on loop entry. + If <literal>REVERSE</> is specified then the step value is subtracted, rather than added, after each iteration. </para> @@ -1785,17 +1786,15 @@ END LOOP <optional> <replaceable>label</replaceable> </optional>; Some examples of integer <literal>FOR</> loops: <programlisting> FOR i IN 1..10 LOOP - -- some computations here - RAISE NOTICE 'i is %', i; + -- i will take on the values 1,2,3,4,5,6,7,8,9,10 within the loop END LOOP; FOR i IN REVERSE 10..1 LOOP - -- some computations here + -- i will take on the values 10,9,8,7,6,5,4,3,2,1 within the loop END LOOP; FOR i IN REVERSE 10..1 BY 2 LOOP - -- some computations here - RAISE NOTICE 'i is %', i; + -- i will take on the values 10,8,6,4,2 within the loop END LOOP; </programlisting> </para> @@ -1805,6 +1804,13 @@ END LOOP; in the <literal>REVERSE</> case), the loop body is not executed at all. No error is raised. </para> + + <para> + If a <replaceable>label</replaceable> is attached to the + <literal>FOR</> loop then the integer loop variable can be + referenced with a qualified name, using that + <replaceable>label</replaceable>. + </para> </sect3> </sect2> @@ -3654,6 +3660,18 @@ a_output := a_output || $$ if v_$$ || referrer_keys.kind || $$ like '$$ </para> </listitem> + <listitem> + <para> + Integer <command>FOR</> loops with <literal>REVERSE</> work + differently: <application>PL/SQL</> counts down from the second + number to the first, while <application>PL/pgSQL</> counts down + from the first number to the second, requiring the loop bounds + to be swapped when porting. This incompatibility is unfortunate + but is unlikely to be changed. (See <xref + linkend="plpgsql-integer-for">.) + </para> + </listitem> + </itemizedlist> </para> |