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Re: O'Reilly interview with Date

From: David Cressey <david.cressey_at_earthlink.net>
Date: Thu, 11 Aug 2005 23:59:31 GMT
Message-ID: <DDRKe.4275$RZ2.106@newsread3.news.atl.earthlink.net>

"Marshall Spight" <marshall.spight_at_gmail.com> wrote in message news:1123693335.220521.200510_at_g47g2000cwa.googlegroups.com...

> I don't think the "overloading" argument is quite right; you
> necessarily have to unify the column namespaces when you join,
> unless you don't want to enforce any column naming discipline
> at all (that is, allow columns with no names, or illegal names,
> or two columns with the same name) which I don't think is tenable.
>
> The namespace unification issue matches quite well with the
> predicate logic model as well; when you do some logical
> operation on two propositions, you necessarily have to unify
> their predicate's namespaces.

Well, I'm not arguing against namespace unification as such. I just think it shouldn't be done on the column names.

>
> The idea of joining only on FK or some references constraint
> is attractive, but I'm not sure if it's general enough. Sometimes
> you want to join Tables A, B, and C, where B and C both reference
> the primary key of A. What would that do? Or what if a table
> references a primary key twice?
>

If a table contains two references to the same primary key, then a natural join would join the reference table in twice, wouldn't it?

>
> Marshall
>
Received on Thu Aug 11 2005 - 18:59:31 CDT

Original text of this message

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