diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/syntax.sgml | 32 |
1 files changed, 19 insertions, 13 deletions
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml index e3dbc4b5ea5..4fe872290a6 100644 --- a/doc/src/sgml/syntax.sgml +++ b/doc/src/sgml/syntax.sgml @@ -1730,10 +1730,10 @@ SELECT string_agg(a ORDER BY a, ',') FROM table; -- incorrect The syntax of a window function call is one of the following: <synopsis> -<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> ) <replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable> -<replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> ) +<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> ) <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable> +<replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> ) </synopsis> where <replaceable class="parameter">window_definition</replaceable> has the syntax @@ -1768,15 +1768,14 @@ UNBOUNDED FOLLOWING <para> <replaceable>window_name</replaceable> is a reference to a named window specification defined in the query's <literal>WINDOW</literal> clause. - Named window specifications are usually referenced with just - <literal>OVER</> <replaceable>window_name</replaceable>, but it is - also possible to write a window name inside the parentheses and then - optionally supply an ordering clause and/or frame clause (the referenced - window must lack these clauses, if they are supplied here). - This latter syntax follows the same rules as modifying an existing - window name within the <literal>WINDOW</literal> clause; see the - <xref linkend="sql-select"> reference - page for details. + Alternatively, a full <replaceable>window_definition</replaceable> can + be given within parentheses, using the same syntax as for defining a + named window in the <literal>WINDOW</literal> clause; see the + <xref linkend="sql-select"> reference page for details. It's worth + pointing out that <literal>OVER wname</> is not exactly equivalent to + <literal>OVER (wname)</>; the latter implies copying and modifying the + window definition, and will be rejected if the referenced window + specification includes a frame clause. </para> <para> @@ -1854,11 +1853,18 @@ UNBOUNDED FOLLOWING </para> <para> + If <literal>FILTER</literal> is specified, then only the input + rows for which the <replaceable>filter_clause</replaceable> + evaluates to true are fed to the window function; other rows + are discarded. Only aggregate window functions accept + a <literal>FILTER</literal> clause. + </para> + + <para> The built-in window functions are described in <xref linkend="functions-window-table">. Other window functions can be added by the user. Also, any built-in or user-defined aggregate function can be - used as a window function. Only aggregate window functions accept - a <literal>FILTER</literal> clause. + used as a window function. </para> <para> |