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Diffstat (limited to 'doc/src/sgml/syntax.sgml')
| -rw-r--r-- | doc/src/sgml/syntax.sgml | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml index 97020845b50..74cc813a681 100644 --- a/doc/src/sgml/syntax.sgml +++ b/doc/src/sgml/syntax.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.106 2006/03/10 19:10:49 momjian Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.107 2006/06/26 17:24:40 tgl Exp $ --> <chapter id="sql-syntax"> <title>SQL Syntax</title> @@ -1571,6 +1571,31 @@ SELECT ROW(1,2.5,'this is a test'); </para> <para> + A row constructor can include the syntax + <replaceable>rowvalue</replaceable><literal>.*</literal>, + which will be expanded to a list of the elements of the row value, + just as occurs when the <literal>.*</> syntax is used at the top level + of a <command>SELECT</> list. For example, if table <literal>t</> has + columns <literal>f1</> and <literal>f2</>, these are the same: +<programlisting> +SELECT ROW(t.*, 42) FROM t; +SELECT ROW(t.f1, t.f2, 42) FROM t; +</programlisting> + </para> + + <note> + <para> + Before <productname>PostgreSQL</productname> 8.2, the + <literal>.*</literal> syntax was not expanded, so that writing + <literal>ROW(t.*, 42)</> created a two-field row whose first field + was another row value. The new behavior is usually more useful. + If you need the old behavior of nested row values, write the inner + row value without <literal>.*</literal>, for instance + <literal>ROW(t, 42)</>. + </para> + </note> + + <para> By default, the value created by a <literal>ROW</> expression is of an anonymous record type. If necessary, it can be cast to a named composite type — either the row type of a table, or a composite type @@ -1619,7 +1644,7 @@ SELECT getf1(CAST(ROW(11,'this is a test',2.5) AS myrowtype)); <programlisting> SELECT ROW(1,2.5,'this is a test') = ROW(1, 3, 'not the same'); -SELECT ROW(a, b, c) IS NOT NULL FROM table; +SELECT ROW(table.*) IS NULL FROM table; -- detect all-null rows </programlisting> For more detail see <xref linkend="functions-comparisons">. Row constructors can also be used in connection with subqueries, |