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Re: Planning for improved versions of IN/NOT IN

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Mike Mascari <mascarm(at)mascari(dot)com>
Cc: Joe Conway <mail(at)joeconway(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Planning for improved versions of IN/NOT IN
Date: 2002-11-30 05:44:59
Message-ID: 27336.1038635099@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Mike Mascari <mascarm(at)mascari(dot)com> writes:
> I curious if any of the rewriting of EXISTS and NOT EXISTS would 
> address the problem described by Date:

> http://www.firstsql.com/iexist.htm

We are not here to redefine the SQL spec ... and especially not to
eliminate its concept of NULL, which is what Date would really like ;-)

The above-quoted screed is based on a claimed logical equivalence
between NOT EXISTS() and NOT IN() that is just plain wrong when you
consider the possibility of NULLs.  Rather than "FirstSQL correctly
processes this query", you should read "FirstSQL deliberately violates
the SQL spec".  (There may be grounds to argue that the spec behavior
could be improved, but that's an argument to be making to the standards
committee, not here.)

			regards, tom lane

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