Re: Nullology of empty strings

From: Steve Kass <skass_at_drew.edu>
Date: Wed, 08 Jan 2003 00:08:27 -0500
Message-ID: <avgbl0$6sc$1@slb6.atl.mindspring.net>

Theory and the ANSI/ISO standards, as far as I know, both make a clear distinction between the known value '' and the value NULL, which often makes best sense to think of as meaning UNKNOWN. If you want to know why the designers of Oracle made this choice, you might post the question in an Oracle newsgroup. Personally, I wouldn't spend any time trying to develop a theory accommodating this idiosyncracy - I don't see how it could make any sense. For example, 'abc' || NULL should be NULL, and 'abc' || '' should be 'abc'. WHERE 'abc' NOT IN (NULL) should filter out everything, but WHERE 'abc' NOT IN ('') should filter out nothing...

Steve Kass
Drew University

Morten wrote:

>Hi. I'm curious about why the empty string '' IS NULL in Oracle databases.
>Is this a general convention? Where can I read up on the theory behind this?
>
>I would like to find out why this is so, and what the theoretical foundations
>are (relational calculus possibly?)
>
>Thanks,
>
>Morten
>
>
Received on Tue Jan 07 2003 - 23:08:27 CST