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From: "vc" <boston103@hotmail.com>
Newsgroups: comp.databases.theory
Subject: Re: So what's null then if it's not nothing?
Date: 29 Nov 2005 05:53:30 -0800
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Xref: dp-news.maxwell.syr.edu comp.databases.theory:34738


Jon Heggland wrote:
[...]
> SQL is confused, and breeds confusion. For one thing, NULL is not a
> value. If it were, it would be equal to itself.

With respect to nulls,  SQL is no more confused that Codd's original
work on which SQL's null treatment is based.  There is no need to
attack SQL whose deficiencies are well known if all one wants to
discuss is the notion of null..

>
> > Whether or not two values are considered distinct  is irrelevant to the
> > null = null comparison.
>
> By SQL fiat, perhaps. But *should* it be? What gives SQL the right to
> redefine notions of equality and "distinctness" in this manner? Or never
> mind the right; does it make *sense*? Is it worth the price?

null=null evaluates to unknown according to the 3vl logic rules.

Again, SQL per se does not have much to do with the notion of null.
Please see Codd's article I mentioned earlier and comment on it rather
that criticizing SQL.

> 
> By the way, is NULL = NULL a valid SQL expression now?
> -- 
> Jon