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Re: weird results from trivial SELECT statement

From: "Oliveiros d'Azevedo Cristina" <oliveiros(dot)cristina(at)marktest(dot)pt>
To: "Lonni J Friedman" <netllama(at)gmail(dot)com>,<pgsql-novice(at)postgresql(dot)org>
Subject: Re: weird results from trivial SELECT statement
Date: 2011-04-27 16:47:09
Message-ID: 7A65A3A9461D4DF79077964EA5D0ADE0@marktestcr.marktest.pt (view raw or flat)
Thread:
Lists: pgsql-novice
From my knowledge, I think that NULL is not a value, it's rather the absense 
of a value.
It doesn't matter if you use = or !=,  testing 'disabled' against a NULL 
column will always fail.

Why dont you try a WHERE clause like
WHERE active != 'disabled
OR active IS NULL
if you want the NULL records as well.

HTH,


Best,
Oliveiros


----- Original Message ----- 
From: "Lonni J Friedman" <netllama(at)gmail(dot)com>
To: <pgsql-novice(at)postgresql(dot)org>
Sent: Wednesday, April 27, 2011 5:25 PM
Subject: [NOVICE] weird results from trivial SELECT statement


> Greetings,
> I've got a Postgresql-8.4.x instance with a bunch of tables taht have
> a text column (called 'active') that can contain any one of the
> following values:
> NULL
> 'disabled'
> <some other text string>
>
> When I run the following query, it seems to ignore NULL values:
> SELECT * FROM mytbl WHERE active!='disabled'
>
> and only returns rows where active!='disabled' AND active IS NOT NULL.
> Is postgresql implicitly assuming that I want non-NULL values?
>
> I can provide additional information, if requested.
>
> thanks!
>
> -- 
> Sent via pgsql-novice mailing list (pgsql-novice(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-novice 


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Subject: Re: weird results from trivial SELECT statement
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