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Add IS UNKNOWN, IS NOT UNKNOWN boolean tests, fix the existing boolean

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tests to return the correct results per SQL9x when given NULL inputs.
Reimplement these tests as well as IS [NOT] NULL to have their own
expression node types, instead of depending on special functions.
From Joe Conway, with a little help from Tom Lane.
This commit is contained in:
Tom Lane
2001-06-19 22:39:12 +00:00
parent 8c30aca2ba
commit 116d2bba7e
18 changed files with 666 additions and 153 deletions
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17
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.61 2001/06/15 21:03:07 tgl Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.62 2001/06/19 22:39:08 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -273,6 +273,21 @@
<productname>Microsoft Access</productname>) to work, but this may
be discontinued in a future release.
</para>
<para>
Boolean values can be tested using the constructs
<synopsis>
<replaceable>expression</replaceable> IS TRUE
<replaceable>expression</replaceable> IS NOT TRUE
<replaceable>expression</replaceable> IS FALSE
<replaceable>expression</replaceable> IS NOT FALSE
<replaceable>expression</replaceable> IS UNKNOWN
<replaceable>expression</replaceable> IS NOT UNKNOWN
</synopsis>
These are similar to <literal>IS NULL</literal> in that they will
always return TRUE or FALSE, never NULL, even when the operand is NULL.
A NULL input is treated as the logical value UNKNOWN.
</para>
</sect1>

4
doc/src/sgml/syntax.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.42 2001/05/12 22:51:35 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.43 2001/06/19 22:39:08 tgl Exp $
-->
<chapter id="sql-syntax">
@ -1060,7 +1060,7 @@ SELECT (5 !) - 6;
<row>
<entry><token>IS</token></entry>
<entry></entry>
<entry>test for TRUE, FALSE, NULL</entry>
<entry>test for TRUE, FALSE, UNKNOWN, NULL</entry>
</row>
<row>