Re: NULL with IN-Clause

From: Philip Lijnzaad <lijnzaad_at_ebi.ac.uk>
Date: 11 May 1999 15:18:13 +0100
Message-ID: <u7wvyflmfu.fsf@ebi.ac.uk>

On Tue, 11 May 1999 13:11:42 GMT,
"James" == James Lorenzen <james_lorenzen_at_allianzlife.com> writes:

James> A NULL is an unknown value.

is that 'known to unknown', or 'unknown to be known', or 'unknown to be unknown' ... :-) NULLs are, of course, useful but ocasionally dubious.

James> That means a NULL is never equal to anything, not even another NULL.
James> It also means that a NULL is never not equal to anything.  IE NULL =
James> NULL evaluates to FALSE, therefore the IN clause with a NULL in the
James> value list will never return a NULL value.

I know, I know. I argue that having NULL in an IN construct is meaningless, and an error should be raised.

At the same time, some database vendors (e.g. Sybase) *do* retrieve rows being NULL when NULL is part of an IN construct. So, who's right and who's wrong ? Cheers,

                                                                      Philip

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Philip Lijnzaad, lijnzaad_at_ebi.ac.uk | European Bioinformatics Institute


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Received on Tue May 11 1999 - 09:18:13 CDT