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Re: So what's null then if it's not nothing?

From: vc <boston103_at_hotmail.com>
Date: 26 Nov 2005 13:36:18 -0800
Message-ID: <1133040978.145734.282720@z14g2000cwz.googlegroups.com>


Jon Heggland wrote:
> In article <1132926804.625596.34020_at_g47g2000cwa.googlegroups.com>,
> boston103_at_hotmail.com says...
> >
> > michael_at_preece.net wrote:
> > [...]
> > >
> > > Any two variables/"fields" (of any type) with "no value at all" are,
> > > indeed, equal.
> > >
> > > Mike.
> >
> > Cute.
>
> "Cute"?
>
> > So, using your valuation for equality, would a query asking for a
> > pairwise list of people living in the same country produce a correct
> > result if some pairs that happen to have nulls for their countries ?
>
> That, of course, depends on what you mean by a correct result, what it
> means that country is NULL, and how the query is formulated.

By the correct result I mean the result that would not claim that people [about whose location we have no clue] live in the same place. Sort of obvious, no ?

>
> If we assume that it is not generally the case that two people with
> NULLs for their countries (speaking loosely here) live in the same
> country, the query would simply have to be written so as to disregard
> people with NULL country.

So you insist that the valuation of "null=null" as true can make sense in some cases ? If so, what are those cases ? If not so, why do we need to modify our query at all ? The standard SQL does not evaluate null=null to true, so why bother writing the query "so as to disregard people with NULL country" ?

> --
> Jon
Received on Sat Nov 26 2005 - 15:36:18 CST

Original text of this message

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