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Date: Thu, 22 May 2003 15:25:56 -0700 (PDT)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Don Park <donp+postgresql@klickitat.st>
Cc: <pgsql-sql@postgresql.org>
Subject: Re: numeric fields and null
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On Thu, 22 May 2003, Don Park wrote:

> Im trying to pull out all records in a table where field
> 'postaladdressid=null' but I cant figure this out.
>
> \d users
> ....
> id               | numeric
> postaladdressid  | numeric
> ....
>
> adhoc=# update users set postaladdressid=null where id=50;
> UPDATE 1
>
> adhoc=# select id,postaladdressid from users where postaladdressid=null;
>  id | postaladdressid
> ----+-----------------
> (0 rows)
>
> Why did it not select record 50?

Because NULL=NULL is not true (it's unknown).  Use IS NULL if you want to
see if something is NULL.