diff options
Diffstat (limited to 'doc/src/sgml/func/func-window.sgml')
| -rw-r--r-- | doc/src/sgml/func/func-window.sgml | 38 |
1 files changed, 23 insertions, 15 deletions
diff --git a/doc/src/sgml/func/func-window.sgml b/doc/src/sgml/func/func-window.sgml index cce0165b952..bcf755c9ebc 100644 --- a/doc/src/sgml/func/func-window.sgml +++ b/doc/src/sgml/func/func-window.sgml @@ -140,7 +140,7 @@ </indexterm> <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type> <optional>, <parameter>offset</parameter> <type>integer</type> - <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) + <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional> <returnvalue>anycompatible</returnvalue> </para> <para> @@ -165,7 +165,7 @@ </indexterm> <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type> <optional>, <parameter>offset</parameter> <type>integer</type> - <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) + <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional> <returnvalue>anycompatible</returnvalue> </para> <para> @@ -188,7 +188,7 @@ <indexterm> <primary>first_value</primary> </indexterm> - <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional> <returnvalue>anyelement</returnvalue> </para> <para> @@ -202,7 +202,7 @@ <indexterm> <primary>last_value</primary> </indexterm> - <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional> <returnvalue>anyelement</returnvalue> </para> <para> @@ -216,7 +216,7 @@ <indexterm> <primary>nth_value</primary> </indexterm> - <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) + <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional> <returnvalue>anyelement</returnvalue> </para> <para> @@ -265,18 +265,26 @@ Other frame specifications can be used to obtain other effects. </para> + <para> + The <literal>null treatment</literal> option must be one of: +<synopsis> + RESPECT NULLS + IGNORE NULLS +</synopsis> + If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL + values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values. + This option is only allowed for the following functions: <function>lag</function>, + <function>lead</function>, <function>first_value</function>, <function>last_value</function>, + <function>nth_value</function>. + </para> + <note> <para> - The SQL standard defines a <literal>RESPECT NULLS</literal> or - <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>, - <function>first_value</function>, <function>last_value</function>, and - <function>nth_value</function>. This is not implemented in - <productname>PostgreSQL</productname>: the behavior is always the - same as the standard's default, namely <literal>RESPECT NULLS</literal>. - Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal> - option for <function>nth_value</function> is not implemented: only the - default <literal>FROM FIRST</literal> behavior is supported. (You can achieve - the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal> + The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal> + option for <function>nth_value</function>. This is not implemented in + <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal> + behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by + reversing the <literal>ORDER BY</literal> ordering.) </para> </note> |