Re: more on delete from join

From: paul c <>
Date: Wed, 26 Aug 2009 21:14:28 GMT
Message-ID: <UAhlm.40815$Db2.39266_at_edtnps83>

Tegiri Nenashi wrote:
> On Aug 26, 1:03 pm, paul c <> wrote:

>> I meant "AND" as the logical connective, not shorthand for relational
>> "<AND>".  "R AND A" stands for a logical conjunction of propositions,
>> each proposition having been concluded to be true.  

> Stop right there. You were writing R UNION A, so R and A are relations
> (or predicates) and not propositions. ...

Okay, I'll stop right there and be even more precise, relations are not predicates, they are representations of predicates. Actually, it is precision that enables the conclusion from two different representations, because they are both representations of the same things - propositions. R <OR> A represents the statement "the tuple(s) in R stand for true propositions OR the tuple(s) in A stand for true proposiitions". If R2 = R <OR> A, then R2 represents the statement "all the tuples in R2 stand for true propositions". Received on Wed Aug 26 2009 - 23:14:28 CEST

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