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2 | | -$Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.1 2002/07/30 19:36:10 momjian Exp $ |
| 2 | +$Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.2 2002/08/20 05:28:23 momjian Exp $ |
3 | 3 | --> |
4 | 4 |
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5 | 5 | <chapter id="plpgsql"> |
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126 | 126 | them to define operators or use them in functional indexes. |
127 | 127 | </para> |
128 | 128 | <sect2 id="plpgsql-advantages"> |
129 | | - <title>Advantages of Using PL/pgSQL</title> |
| 129 | + <title>Advantages of Using<application>PL/pgSQL</application></title> |
130 | 130 |
|
131 | 131 | <itemizedlist> |
132 | 132 | <listitem> |
@@ -852,10 +852,58 @@ SELECT INTO <replaceable>target</replaceable> <replaceable>expressions</replacea |
852 | 852 | </para> |
853 | 853 |
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854 | 854 | <para> |
855 | | - There is a special variable named FOUND of type |
856 | | - <type>boolean</type> that can be used immediately after a SELECT |
857 | | - INTO to check if an assignment had success (that is, at least one |
858 | | - row was returned by the SELECT). For example, |
| 855 | + There is a special variable named <literal>FOUND</literal> of |
| 856 | + type <type>boolean</type>. The initial value of |
| 857 | + <literal>FOUND</literal> is false; it is set to true when one of |
| 858 | + the following events occurs: |
| 859 | + <itemizedlist> |
| 860 | + <listitem> |
| 861 | + <para> |
| 862 | +A SELECT INTO statement is executed, and it returns one or |
| 863 | +more rows. |
| 864 | + </para> |
| 865 | + </listitem> |
| 866 | + <listitem> |
| 867 | + <para> |
| 868 | +A UPDATE, INSERT, or DELETE statement is executed, and it |
| 869 | +affects one or more rows. |
| 870 | + </para> |
| 871 | + </listitem> |
| 872 | + <listitem> |
| 873 | + <para> |
| 874 | +A PERFORM statement is executed, and it discards one or more |
| 875 | +rows. |
| 876 | + </para> |
| 877 | + </listitem> |
| 878 | + <listitem> |
| 879 | + <para> |
| 880 | +A FETCH statement is executed, and it returns an additional |
| 881 | +row. |
| 882 | + </para> |
| 883 | + </listitem> |
| 884 | + <listitem> |
| 885 | + <para> |
| 886 | +A FOR statement is executed, and it iterates one or more |
| 887 | +times. This applies to all three variants of the FOR statement |
| 888 | +(integer FOR loops, record-set FOR loops, and dynamic |
| 889 | +record-set FOR loops). <literal>FOUND</literal> is only set |
| 890 | +when the FOR loop exits: inside the execution of the loop, |
| 891 | +<literal>FOUND</literal> is not modified, although it may be |
| 892 | +set by the execution of other statements. |
| 893 | + </para> |
| 894 | + </listitem> |
| 895 | + </itemizedlist> |
| 896 | + If none of these events occur, <literal>FOUND</literal> is set to |
| 897 | + false. <literal>FOUND</literal> is a local variable; any changes |
| 898 | + to it effect only the current <application>PL/pgSQL</application> |
| 899 | + function. |
| 900 | +</para> |
| 901 | + |
| 902 | +<para> |
| 903 | + You can use <literal>FOUND</literal> immediately after a SELECT |
| 904 | + INTO statement to determine whether the assignment was successful |
| 905 | + (that is, at least one row was was returned by the SELECT |
| 906 | + statement). For example: |
859 | 907 |
|
860 | 908 | <programlisting> |
861 | 909 | SELECT INTO myrec * FROM EMP WHERE empname = myname; |
@@ -902,10 +950,10 @@ PERFORM <replaceable>query</replaceable>; |
902 | 950 |
|
903 | 951 | This executes a <literal>SELECT</literal> |
904 | 952 | <replaceable>query</replaceable> and discards the |
905 | | - result. <application>PL/pgSQL</application> variables are substituted |
906 | | - in the query as usual. Also, the special variable FOUND is set to |
907 | | - true if the query produced at least one row, or false if it produced |
908 | | - no rows. |
| 953 | + result. <application>PL/pgSQL</application> variables are |
| 954 | +substitutedin the query as usual. Also, the special variable |
| 955 | +<literal>FOUND</literal> is set totrue if the query produced at |
| 956 | +least one row, or false if it producedno rows. |
909 | 957 | </para> |
910 | 958 |
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911 | 959 | <note> |
@@ -1638,8 +1686,8 @@ FETCH <replaceable>cursor</replaceable> INTO <replaceable>target</replaceable>; |
1638 | 1686 | FETCH retrieves the next row from the cursor into a target, |
1639 | 1687 | which may be a row variable, a record variable, or a comma-separated |
1640 | 1688 | list of simple variables, just like SELECT INTO. As with |
1641 | | -SELECT INTO, the special variable FOUND may be checked to see |
1642 | | -whether a row was obtained or not. |
| 1689 | +SELECT INTO, the special variable<literal>FOUND</literal> may be |
| 1690 | +checked to seewhether a row was obtained or not. |
1643 | 1691 |
|
1644 | 1692 | <programlisting> |
1645 | 1693 | FETCH curs1 INTO rowvar; |
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