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

From: Jon Heggland <heggland_at_idi.ntnu.no>
Date: Mon, 28 Nov 2005 09:48:07 +0100
Message-ID: <MPG.1df4e2af74dac413989710@news.ntnu.no>


In article <1133114041.839154.239970_at_g47g2000cwa.googlegroups.com>, boston103_at_hotmail.com says...
> Jon Heggland wrote:
> [...]
> >
> > I prefer to avoid NULLs altogether. But as I'm sure you know, even SQL
> > considers NULLs equal in many circumstances.
>
> Well, I do not know that. Could you give an example other than "order
> by"

Off the top of my head: Projection, and in some cases the UNIQUE constraint.

> (which by the way does not involve comparison between null
> attributes at least at the logical level) ?

How so?

> > > 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" ?
> >
> > To avoid 3VL.
>
> If you said, "to avoid 3vl SQL implementation inconsistencies", I'd
> agree ;)

Fair enough. I'm skeptical to 3VL, even if it were consistent. It's complicated and unintuitive.

-- 
Jon
Received on Mon Nov 28 2005 - 02:48:07 CST

Original text of this message

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