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Diffstat (limited to 'doc/src/sgml/xfunc.sgml')
| -rw-r--r-- | doc/src/sgml/xfunc.sgml | 56 |
1 files changed, 55 insertions, 1 deletions
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml index a5fb62e18b9..44c83e8dbc7 100644 --- a/doc/src/sgml/xfunc.sgml +++ b/doc/src/sgml/xfunc.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.133 2008/10/31 19:37:56 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.134 2008/12/04 17:51:26 petere Exp $ --> <sect1 id="xfunc"> <title>User-Defined Functions</title> @@ -663,6 +663,60 @@ SELECT mleast(VARIADIC ARRAY[10, -1, 5, 4.4]); </para> </sect2> + <sect2 id="xfunc-parameter-defaults"> + <title><acronym>SQL</> Functions with Parameters Default Values</title> + + <indexterm> + <primary>default values</primary> + </indexterm> + + <para> + Functions can be declared with parameters with default values or + expressions. The default expressions are used as parameter value + if the parameter is not explicitly specified in a function call. + All parameters after a a parameter with default value have to be + parameters with default values as well. + </para> + + <para> + For example: +<screen> +CREATE FUNCTION foo(a int DEFAULT 1, b int DEFAULT 2, c int DEFAULT 3) +RETURNS int +LANGUAGE SQL +AS $$ + SELECT $1 + $2 + $3; +$$; + +SELECT foo(10, 20, 30); + foo +----- + 60 +(1 row) + +SELECT foo(10, 20); + foo +----- + 33 +(1 row) + +SELECT foo(10); + foo +----- + 15 +(1 row) + +SELECT foo(); + foo +----- + 6 +(1 row) +</screen> + Instead of the key word <literal>DEFAULT</literal>, + the <literal>=</literal> sign can also be used. + </para> + </sect2> + <sect2 id="xfunc-sql-table-functions"> <title><acronym>SQL</acronym> Functions as Table Sources</title> |