diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/plpgsql.sgml | 72 |
1 files changed, 60 insertions, 12 deletions
diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml index 9a58e6b8e3b..3e90f32665d 100644 --- a/doc/src/sgml/plpgsql.sgml +++ b/doc/src/sgml/plpgsql.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.1 2002/07/30 19:36:10 momjian Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.2 2002/08/20 05:28:23 momjian Exp $ --> <chapter id="plpgsql"> @@ -126,7 +126,7 @@ END; them to define operators or use them in functional indexes. </para> <sect2 id="plpgsql-advantages"> - <title>Advantages of Using PL/pgSQL</title> + <title>Advantages of Using <application>PL/pgSQL</application></title> <itemizedlist> <listitem> @@ -852,10 +852,58 @@ SELECT INTO <replaceable>target</replaceable> <replaceable>expressions</replacea </para> <para> - There is a special variable named FOUND of type - <type>boolean</type> that can be used immediately after a SELECT - INTO to check if an assignment had success (that is, at least one - row was returned by the SELECT). For example, + There is a special variable named <literal>FOUND</literal> of + type <type>boolean</type>. The initial value of + <literal>FOUND</literal> is false; it is set to true when one of + the following events occurs: + <itemizedlist> + <listitem> + <para> + A SELECT INTO statement is executed, and it returns one or + more rows. + </para> + </listitem> + <listitem> + <para> + A UPDATE, INSERT, or DELETE statement is executed, and it + affects one or more rows. + </para> + </listitem> + <listitem> + <para> + A PERFORM statement is executed, and it discards one or more + rows. + </para> + </listitem> + <listitem> + <para> + A FETCH statement is executed, and it returns an additional + row. + </para> + </listitem> + <listitem> + <para> + A FOR statement is executed, and it iterates one or more + times. This applies to all three variants of the FOR statement + (integer FOR loops, record-set FOR loops, and dynamic + record-set FOR loops). <literal>FOUND</literal> is only set + when the FOR loop exits: inside the execution of the loop, + <literal>FOUND</literal> is not modified, although it may be + set by the execution of other statements. + </para> + </listitem> + </itemizedlist> + If none of these events occur, <literal>FOUND</literal> is set to + false. <literal>FOUND</literal> is a local variable; any changes + to it effect only the current <application>PL/pgSQL</application> + function. + </para> + + <para> + You can use <literal>FOUND</literal> immediately after a SELECT + INTO statement to determine whether the assignment was successful + (that is, at least one row was was returned by the SELECT + statement). For example: <programlisting> SELECT INTO myrec * FROM EMP WHERE empname = myname; @@ -902,10 +950,10 @@ PERFORM <replaceable>query</replaceable>; This executes a <literal>SELECT</literal> <replaceable>query</replaceable> and discards the - result. <application>PL/pgSQL</application> variables are substituted - in the query as usual. Also, the special variable FOUND is set to - true if the query produced at least one row, or false if it produced - no rows. + result. <application>PL/pgSQL</application> variables are + substituted in the query as usual. Also, the special variable + <literal>FOUND</literal> is set to true if the query produced at + least one row, or false if it produced no rows. </para> <note> @@ -1638,8 +1686,8 @@ FETCH <replaceable>cursor</replaceable> INTO <replaceable>target</replaceable>; FETCH retrieves the next row from the cursor into a target, which may be a row variable, a record variable, or a comma-separated list of simple variables, just like SELECT INTO. As with - SELECT INTO, the special variable FOUND may be checked to see - whether a row was obtained or not. + SELECT INTO, the special variable <literal>FOUND</literal> may be + checked to see whether a row was obtained or not. <programlisting> FETCH curs1 INTO rowvar; |