From 5932915fef5a3fce0267de390650fd98b4a3d824 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 9 Dec 2008 20:52:03 +0000
Subject: [PATCH] Add a specific example of parenthesizing when extracting a
field of a composite column. Might help cut down on future questions...
---
doc/src/sgml/syntax.sgml | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 90aa3b6c9b4..cca44794340 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 1.125 2008/10/29 14:35:04 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.126 2008/12/09 20:52:03 tgl Exp $ -->
<chapter id="sql-syntax">
<title>SQL Syntax</title>
@@ -1387,7 +1387,18 @@ $1.somecolumn
</programlisting>
(Thus, a qualified column reference is actually just a special case
- of the field selection syntax.)
+ of the field selection syntax.) An important special case is
+ extracting a field from a table column that is of a composite type:
+
+<programlisting>
+(compositecol).somefield
+(mytable.compositecol).somefield
+</programlisting>
+
+ The parentheses are required here to show that
+ <structfield>compositecol</> is a column name not a table name,
+ or that <structname>mytable</> is a table name not a schema name
+ in the second case.
</para>
</sect2>
--
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