Re: Does Codd's view of a relational database differ from that ofDate& Darwin? [M.Gittens]

From: Paul <paul_at_test.com>
Date: Mon, 06 Jun 2005 16:23:13 +0100
Message-ID: <42a46a61$0$1696$ed2e19e4@ptn-nntp-reader04.plus.net>

Alfredo Novoa wrote:

>>I guess the other claim against NULLs is that they make things more
>>complex and less intuitive, which is a more subjective point. You could
>>argue that Darwen's method of avoiding NULLs is more complex that using
>>NULLs in the first place.

>
> Nulls undermine the conceptual integrity of the Relational Model which
> is based in predicate logic.
>
> A tuple with nulls does not match to a logical proposition.
>
> This causes many problems. Some of them were pointed by Eric.

OK so basically the problem is with aggregates?

Why not say then that all aggregates that involve a NULL return NULL?

And if you want an actual result, you must specify an explicit behaviour by the use of COALESCE or WHERE clauses.

So could this actually be another problem with SQL's treatment of NULLs rather than with NULLs per se?

Paul. Received on Mon Jun 06 2005 - 10:23:13 CDT