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Date: Wed, 08 Aug 2007 09:26:08 -0300
From: Bob Badour <bbadour@pei.sympatico.ca>
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Newsgroups: comp.databases.theory
Subject: Re: NULLs:  theoretical problems?
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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.