Re: more on delete from join

From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 29 Aug 2009 00:33:30 GMT
Message-ID: <uH_lm.43016$PH1.35389_at_edtnps82>


Mr. Scott wrote:
...
> I don't need to look. <AND> is a relational operator; AND is a logical
> operator. They are related only because the predicate of the result of
> <AND> is the conjunction of the predicates of its operands.

Actually, <AND> is not the logical conjunction of predicates, but the join or 'conjoin' (of relations) as D&D carefully put it, I think to make clear that it is not conjunction of logical predicates. I think they call it a counterpart. This recognizes that the relation form dispenses with some of the details in FOL notation. I suspect that people who don't master the distinction as well as the indirection needed to interpret results will never be able to see through certain RM problems. Received on Sat Aug 29 2009 - 02:33:30 CEST

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