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Date: Mon, 29 Jan 2007 22:45:43 -0700
From: Michael Fuhr <mike@fuhr.org>
To: Phillip Smith <phillip.smith@weatherbeeta.com.au>
Cc: pgsql-sql@postgresql.org
Subject: Re: Differentiate Between Zero-Length String and NULL Column Values
Message-ID: <20070130054543.GA98994@winnie.fuhr.org>
References: <016d01c74430$043b1b90$9b0014ac@wbaus090>
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On Tue, Jan 30, 2007 at 04:32:22PM +1100, Phillip Smith wrote:
> The second row (401600) is what I'm interested in for this particular
> problem. The problem is when I try and add a WHERE clause:
> 	SELECT * FROM tmpstk WHERE ean = '';
> 	SELECT * FROM tmpstk WHERE TRIM(ean) = '';
> 	SELECT * FROM tmpstk WHERE ean = NULL;
> None of the above queries return any rows.

Checking for equality against NULL won't work unless you have
transform_null_equals set, which you shouldn't.  Use IS NULL instead:

SELECT * FROM tmpstk WHERE ean IS NULL;

-- 
Michael Fuhr