Re: more on delete from join
Date: Sat, 29 Aug 2009 01:44:25 -0400
Message-ID: <O5-dnVazu8GkXQXXnZ2dnUVZ_sydnZ2d_at_giganews.com>
"paul c" <toledobythesea_at_oohay.ac> wrote in message
news: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 didn't say that <AND> is the logical conjunction of predicates. I said that the predicate of the result of <AND> is the logical conjunction of the predicates of its operands. If you still doubt that that is what D&D intended, then I suggest that you revisit the sections "Dispensing with TIMES" and "Dispensing with UNION" on pages 362-363. Received on Sat Aug 29 2009 - 07:44:25 CEST