Re: No exceptions?
From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 30 Jun 2006 22:12:39 GMT
Message-ID: <rlhpg.111313$Mn5.39829_at_pd7tw3no>
>
> I don't know what precisely you mean by "logical flaw", so I'll pass
> judgement. If something should be substituted for x (a "default value",
> so to speak), TABLE_DUM does seem the natural choice, though, as it
> corresponds to false/zero in some sense.
>
>
> "TABLE_DUM join y" evaluates to the empty relation with y's heading, not
> TABLE_DUM (unless y's header is also empty, of course).
Date: Fri, 30 Jun 2006 22:12:39 GMT
Message-ID: <rlhpg.111313$Mn5.39829_at_pd7tw3no>
Jon Heggland wrote:
> paul c wrote:
[Quoted] >> 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).
Right, sorry about that.
p Received on Sat Jul 01 2006 - 00:12:39 CEST