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From:  Jan Hidders <hidders@gmail.com>
Newsgroups: comp.databases.theory
Subject: Re: NULLs: theoretical problems?
Date: Wed, 08 Aug 2007 18:49:26 -0000
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On 8 aug, 17:09, Bob Badour <bbad...@pei.sympatico.ca> wrote:
> Jan Hidders wrote:
> > On 8 aug, 14:26, Bob Badour <bbad...@pei.sympatico.ca> wrote:
>
> >>sinister wrote:
>
> >>>Many discussions point out one deficiency of NULLs:  that they collapse
> >>>multiple, distinct concepts into one ("no value possible," "value missing,"
> >>>"value not available at this time", etc).
>
> >>>What are the other theoretical problems?  My impression from skimming some
> >>>threads in this ng is that some anomalies might occur, maybe having to do
> >>>with NULLs and joins, or NULLs and keys composed of more than one field, but
> >>>I'm not sure.
>
> >>The ultimate theoretical problem is a complete lack of any theory
> >>underpinning NULL.
>
> > Just to avoid any misunderstandings: there has of course been lots of
> > theory on certain interpretations of null values, such as the work by
> > Raymond Reiter and by Joachim Biskup, but not on the specific meaning
> > (if you can call it that) that they were given in SQL. Whether that is
> > necessarily a big problem is IMO not so easy to say.
>
> In other words, some folks accept that NULL exists without any
> theoretical underpinning and then create theories of interpretation.

Indeed. Because, as we all know, proposing and investigating
alternatives is the same as accepting something's existence.

> How
> exactly does that differ from scriptural interpretation and theories
> thereof?

Exactly! Rejecting straight away null values in any form or shape
without any sort of investigation of their properties would have been
much more scientific. :-)

-- Jan Hidders