Date: Tue, 20 Jan 2004 15:33:22 +0100
From: Reinoud van Leeuwen <reinoud.v@n.leeuwen.net>
To: pgsql-sql@postgresql.org
Subject: Re: comparing nulls
Message-ID: <20040120153322.U66382@spoetnik.xs4all.nl>
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References: <04012019131206.01434@thenilgiris.com>
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	from lawgon@thenilgiris.com on Tue, Jan 20, 2004 at 07:13:12PM
	+0530

On Tue, Jan 20, 2004 at 07:13:12PM +0530, Kenneth Gonsalves wrote:
> in postgres7.1 i had a table where an integer field could be null. There was 
> no default value. a select statement like so:
> 'select * from table where field = null' 
> would give all the rows where that field had no value.
> on porting to 7.3.2, this doesnt work. How to do this?

Because NULL can be read as "unknown". It does not make much sense to 
test wheter a value of an integer is numerically equal to unknown. That is 
why there is the IS operator:

where field IS null

-- 
__________________________________________________
"Nothing is as subjective as reality"
Reinoud van Leeuwen    reinoud.v@n.leeuwen.net
http://www.xs4all.nl/~reinoud
__________________________________________________