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Received: by postgres.Berkeley.EDU (5.61/1.29)
	id AA27234; Thu, 5 Mar 92 10:46:36 -0800
Message-Id: <9203051846.AA27234@postgres.Berkeley.EDU>
From: postarch (Postgres Mailing Archive)
Subject: Re: null values in attributes
To: postgres@postgres.berkeley.edu
Sender: pg_adm@postgres.berkeley.edu
Reply-To: mer@postgres.berkeley.edu
In-Reply-To: Your message of "Wed, 04 Mar 92 18:53:30 PST."
             <9203050253.AA19756@postgres.Berkeley.EDU> 
Date: Thu, 05 Mar 92 10:46:19 PST

you write:

> We are trying to retrieve tuples from a class, selecting on a
> attributed that is undefined or null. Here's the query:
> 
> -----------
> Go
> * retrieve (s.all) from s in student where placed_in = NULL
> \g
> 
> Query sent to backend is "retrieve (s.all) from s in student where
> placed_in = NULL "
> Error: No response from the backend, exiting...
> -----------
> 
> As you can see, the monitor hangs for a while and then exits without
> delivering any results. Can anyone tell me what we're doing wrong?
> We greatly appreciate any help.

The problem is that postgres doesn't handle nulls very well.  NULL is
a reserved keyword in the language, so the parser accepts it, but the
backend doesn't know what to do with it and subsequently lays and egg.
Hopefully after 4.0 we can address this problem once and for all.


Jeff Meredith
mer@postgres.berkeley.edu