diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/func.sgml | 35 | ||||
| -rw-r--r-- | doc/src/sgml/typeconv.sgml | 26 |
2 files changed, 53 insertions, 8 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 8c7a48308ec..d7430f1ccf8 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.259 2005/06/24 20:53:29 tgl Exp $ +$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.260 2005/06/26 22:05:35 tgl Exp $ PostgreSQL documentation --> @@ -6901,6 +6901,39 @@ SELECT NULLIF(value, '(none)') ... </sect2> + <sect2> + <title><literal>GREATEST</literal> and <literal>LEAST</literal></title> + + <indexterm> + <primary>GREATEST</primary> + </indexterm> + <indexterm> + <primary>LEAST</primary> + </indexterm> + +<synopsis> +<function>GREATEST</function>(<replaceable>value</replaceable> <optional>, ...</optional>) +</synopsis> +<synopsis> +<function>LEAST</function>(<replaceable>value</replaceable> <optional>, ...</optional>) +</synopsis> + + <para> + The <function>GREATEST</> and <function>LEAST</> functions select the + largest or smallest value from a list of any number of expressions. + The expressions must all be convertible to a common data type, which + will be the type of the result + (see <xref linkend="typeconv-union-case"> for details). NULL values + in the list are ignored. The result will be NULL only if all the + expressions evaluate to NULL. + </para> + + <para> + Note that <function>GREATEST</> and <function>LEAST</> are not in + the SQL standard, but are a common extension. + </para> + </sect2> + </sect1> diff --git a/doc/src/sgml/typeconv.sgml b/doc/src/sgml/typeconv.sgml index ae0e3aea4d7..86e0561acc0 100644 --- a/doc/src/sgml/typeconv.sgml +++ b/doc/src/sgml/typeconv.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/typeconv.sgml,v 1.43 2004/12/23 23:07:38 tgl Exp $ +$PostgreSQL: pgsql/doc/src/sgml/typeconv.sgml,v 1.44 2005/06/26 22:05:36 tgl Exp $ --> <chapter Id="typeconv"> @@ -120,7 +120,7 @@ with, and perhaps converted to, the types of the target columns. </varlistentry> <varlistentry> <term> -<literal>UNION</literal>, <literal>CASE</literal>, and <literal>ARRAY</literal> constructs +<literal>UNION</literal>, <literal>CASE</literal>, and related constructs </term> <listitem> <para> @@ -129,7 +129,8 @@ must appear in a single set of columns, the types of the results of each <command>SELECT</> clause must be matched up and converted to a uniform set. Similarly, the result expressions of a <literal>CASE</> construct must be converted to a common type so that the <literal>CASE</> expression as a whole -has a known output type. The same holds for <literal>ARRAY</> constructs. +has a known output type. The same holds for <literal>ARRAY</> constructs, +and for the <function>GREATEST</> and <function>LEAST</> functions. </para> </listitem> </varlistentry> @@ -782,7 +783,7 @@ padding spaces. </sect1> <sect1 id="typeconv-union-case"> -<title><literal>UNION</literal>, <literal>CASE</literal>, and <literal>ARRAY</literal> Constructs</title> +<title><literal>UNION</literal>, <literal>CASE</literal>, and Related Constructs</title> <indexterm zone="typeconv-union-case"> <primary>UNION</primary> @@ -799,20 +800,31 @@ padding spaces. <secondary>determination of result type</secondary> </indexterm> +<indexterm zone="typeconv-union-case"> + <primary>GREATEST</primary> + <secondary>determination of result type</secondary> +</indexterm> + +<indexterm zone="typeconv-union-case"> + <primary>LEAST</primary> + <secondary>determination of result type</secondary> +</indexterm> + <para> SQL <literal>UNION</> constructs must match up possibly dissimilar types to become a single result set. The resolution algorithm is applied separately to each output column of a union query. The <literal>INTERSECT</> and <literal>EXCEPT</> constructs resolve dissimilar types in the same way as <literal>UNION</>. The -<literal>CASE</> and <literal>ARRAY</> constructs use the identical +<literal>CASE</>, <literal>ARRAY</>, <function>GREATEST</> and +<function>LEAST</> constructs use the identical algorithm to match up their component expressions and select a result data type. </para> <procedure> -<title><literal>UNION</literal>, <literal>CASE</literal>, and -<literal>ARRAY</literal> Type Resolution</title> +<title>Type Resolution for <literal>UNION</literal>, <literal>CASE</literal>, +and Related Constructs</title> <step performance="required"> <para> |