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Re: null != null ???

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: thomas(at)pgsql(dot)com
Cc: Fran Fabrizio <ffabrizio(at)mmrd(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: null != null ???
Date: 2001-10-26 16:34:15
Message-ID: 24842.1004114055@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-general
Thomas Lockhart <lockhart(at)fourpalms(dot)org> writes:
> Yes, this is an explicit feature in our parser to help out poor MSAccess
> souls who have a product which generates illegal SQL queries. We put in
> a specific rule to convert "anything=NULL" to "anything IS NULL", which
> *is* legal syntax.

It should also be noted that as of 7.2, this transformation is optional
(see "transform_null_equals" runtime parameter), and the default is NOT
to make the transformation --- ie, as of 7.2 the default behavior is
SQL-spec-compliant:

regression=# select null = null;
 ?column?
----------

(1 row)

regression=# set transform_null_equals TO 1;
SET VARIABLE
regression=# select null = null;
 ?column?
----------
 t
(1 row)

regression=#

			regards, tom lane

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