From c242502005bb0e89e55a2f1f68cc37b5480b50ad Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 2 Feb 2009 20:42:57 +0000
Subject: [PATCH] Document the longstanding behavior of LIMIT NULL and OFFSET
NULL, per gripe from David Wheeler that this was mentioned nowhere. In
passing, editorialize a bit on the description of the SQL:2008 equivalent
syntax.
---
doc/src/sgml/ref/select.sgml | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index a33a537bd48..ff5d6812604 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -1,5 +1,5 @@
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.119 2009/01/23 14:05:28 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.120 2009/02/02 20:42:57 tgl Exp $
PostgreSQL documentation
-->
@@ -1002,6 +1002,13 @@ OFFSET <replaceable class="parameter">start</replaceable>
class="parameter">count</replaceable> rows to be returned.
</para>
+ <para>
+ If the <replaceable class="parameter">count</replaceable> expression
+ evaluates to NULL, it is treated as <literal>LIMIT ALL</>, i.e., no
+ limit. If <replaceable class="parameter">start</replaceable> evaluates
+ to NULL, it is treated the same as <literal>OFFSET 0</>.
+ </para>
+
<para>
SQL:2008 introduced a different syntax to achieve the same thing,
which PostgreSQL also supports. It is:
@@ -1014,10 +1021,11 @@ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] {
the <literal>FETCH</literal> clause. <literal>ROW</literal>
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
and <literal>NEXT</literal> are noise words that don't influence
- the effects of these clauses. When using expressions other than
- constants for the offset or fetch count, parentheses will be
- necessary in most cases. If the fetch count is omitted, it
- defaults to 1.
+ the effects of these clauses. In this syntax, when using expressions
+ other than simple constants for <replaceable class="parameter">start</>
+ or <replaceable class="parameter">count</replaceable>, parentheses will be
+ necessary in most cases. If <replaceable class="parameter">count</> is
+ omitted in <literal>FETCH</>, it defaults to 1.
</para>
<para>
--
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