diff options
| -rw-r--r-- | doc/src/sgml/queries.sgml | 30 |
1 files changed, 29 insertions, 1 deletions
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml index 67ca71e5649..320d7053cf2 100644 --- a/doc/src/sgml/queries.sgml +++ b/doc/src/sgml/queries.sgml @@ -762,7 +762,8 @@ SELECT * FROM vw_getfoo; In some cases it is useful to define table functions that can return different column sets depending on how they are invoked. To support this, the table function can be declared as returning - the pseudo-type <type>record</type>. When such a function is used in + the pseudo-type <type>record</type> with no <literal>OUT</literal> + parameters. When such a function is used in a query, the expected row structure must be specified in the query itself, so that the system can know how to parse and plan the query. This syntax looks like: @@ -803,6 +804,33 @@ SELECT * that the parser knows, for example, what <literal>*</literal> should expand to. </para> + + <para> + This example uses <literal>ROWS FROM</literal>: +<programlisting> +SELECT * +FROM ROWS FROM + ( + json_to_recordset('[{"a":40,"b":"foo"},{"a":"100","b":"bar"}]') + AS (a INTEGER, b TEXT), + generate_series(1, 3) + ) AS x (p, q, s) +ORDER BY p; + + p | q | s +-----+-----+--- + 40 | foo | 1 + 100 | bar | 2 + | | 3 +</programlisting> + It joins two functions into a single <literal>FROM</literal> + target. <function>json_to_recordset()</function> is instructed + to return two columns, the first <type>integer</type> + and the second <type>text</type>. The result of + <function>generate_series()</function> is used directly. + The <literal>ORDER BY</literal> clause sorts the column values + as integers. + </para> </sect3> <sect3 id="queries-lateral"> |