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Re: No exceptions?

From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Sat, 01 Jul 2006 00:04:36 +0200
Message-ID: <e8479d$ejm$1@orkan.itea.ntnu.no>


paul c wrote:
> Let me re-phrase my original question: Is there a logical flaw in
> substituting TABLE_DUM for x in the expression "x join y" when x is not
> in the catalogue?
>

I don't know what precisely you mean by "logical flaw", so I'll pass judgement. If something should be substituted for x (a "default value", so to speak), TABLE_DUM does seem the natural choice, though, as it corresponds to false/zero in some sense.

> (Assuming that the syntax requires x to be a relation and with the whole
> expression's value being TABLE_DUM as well and granting that such a
> result might seem surprising to most people.)

"TABLE_DUM join y" evaluates to the empty relation with y's heading, not TABLE_DUM (unless y's header is also empty, of course).

-- 
Jon
Received on Fri Jun 30 2006 - 17:04:36 CDT

Original text of this message

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