Subject: Re: silly NULL question
From: Rod Taylor <rbt@rbt.ca>
To: Dan Weeks <danimal@wildbrain.com>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <16160.26749.931319.656882@underdog.wildbrain.com>
References: <16160.26749.931319.656882@underdog.wildbrain.com>
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Date: 24 Jul 2003 19:25:16 -0400

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> Would return the row.  Now with an upgrade to PostgreSQL 7.3 (yes, I know
> there are many changes and we're working through them right now) the same
> query returns nothing.  Dropping the "AND parent_id =3D NULL" returns the=
 row
> as expected.

NULL is similar to UNKNOWN.

So, NULL =3D NULL is the similar to UNKNOWN =3D UNKNOWN.  Since you don't
know it, how can you tell if they're equal or not?

Syntax you're looking for is: AND parent_id IS NULL

If you really really really need =3D NULL (due to some MS product which
ignores SQL standards -- say MS Access) there is a toggle in the
postgresql.conf file to allow automated conversion of =3D NULL to IS NULL
within the server.


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