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Message from discussion Does Codd's view of a relational database differ from that of Date & Darwin? [M.Gittens]
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Jan Hidders  
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 More options Jun 4 2005, 5:30 am
Newsgroups: comp.databases.theory
From: Jan Hidders <jan.hidd...@REMOVETHIS.pandora.be>
Date: Sat, 04 Jun 2005 09:30:15 GMT
Local: Sat, Jun 4 2005 5:30 am
Subject: Re: Does Codd's view of a relational database differ from that of Date & Darwin? [M.Gittens]
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mountain man wrote:

> There have been, there are,
> and there always will be
> NULLS in the real world.

NULLs are an abstraction and like all abstractions they do not really
exist. The relevant question here is if they are necessary and useful to
describe the world.

> Does this fact not conflict
> with Date's wants, and if
> so, why does Date want
> to ignore them?

They unnecessarily complicate the model. Anything that can be modeled
with them can also be modeled without them, and to the extent that they
are convenient this is mostly due to the fact that the possibilities for
user-defined domains were too restricted.

-- Jan Hidders


 
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