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Re: comparing rows

From: The Hermit Hacker <scrappy(at)hub(dot)org>
To: Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Magnus Hagander <mha(at)sollentuna(dot)net>, Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: comparing rows
Date: 2000-08-04 14:43:17
Message-ID: Pine.BSF.4.21.0008041142480.1163-100000@thelab.hub.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, 4 Aug 2000, Thomas Lockhart wrote:

> > > btw, it appears that SQL99 (haven't checked SQL92) specifies that
> > > test=# select (1,2,3) = (1,2,null);
> > >  ?column?
> > > ----------
> > 
> > > (1 row)
> > 
> > > should return FALSE, not NULL.
> > What?  If so, they broke it pretty badly.  This should be equivalent to
> > 1 = 1 AND 2 = 2 AND 3 = NULL, which should reduce to TRUE AND TRUE AND NULL,
> > which should reduce to NULL.  Anything else is not self-consistent.
> 
> Hmm. I could have sworn I looked this up (and was suprised at the
> result). But I'm not finding the example anywhere, and Section 8.2
> General Rule 1 seems to indicate that we do the right thing here
> already.
> 
> Also, I *think* we have settled on the following facts:
> 
> 1) "3 = NULL" is typical of an expression generated by M$ Access.
> 
> 2) "3 = NULL" is *not* legal SQL9x syntax, which specifies "3 IS NULL"
> for the comparison "does three have a value of NULL?".
> 
> 3) New versions of M$ Access continue to generate bogus queries
> containing these comparisons.
> 
> 4) Postgres will continue to understand (at least) the special case of
> "column/value = NULL" to retain compatibility with M$.

Stupid question here ... but ... can't this kludge be "faked" in the ODBC
driver itself, vs in the server? *raised eyebrow*



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