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Re: OO versus RDB

From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Fri, 30 Jun 2006 08:55:39 +0200
Message-ID: <e82i15$i3m$1@orkan.itea.ntnu.no>


J M Davitt wrote:
> In at least one case I know of, select and restrict are
> different: select involves comparison of an attribute
> to some explicit value while restrict involves comparison
> of two attribute values.

For what it's worth: That sounds very strange. A restrict(/select) need not involve any comparison at all. I don't see what possible value such a distinction could have.

> I asked Chris Date about his; he told me, "There's no
> difference" and the two terms seem to be interchangeable
> in virtually all writings.

I guess one reason some people (including me) favour "restrict" over "select" is to avoid confusion with the SELECT part of SQL queries, which does projection (and extension and renaming), not restriction. (The WHERE part does restriction.)

-- 
Jon
Received on Fri Jun 30 2006 - 01:55:39 CDT

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