Re: Codd's Information Principle
From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 31 Oct 2009 04:41:14 GMT
Message-ID: <KdPGm.49955$Db2.33801_at_edtnps83>
>
> This doesn't make sense. Perhaps "one from each operand"?
> If so, yes. The predicate associated with r JOIN s is
> (predicate associated with r) AND (predicate associated with s).
> So each result tuple present makes this true and
> each result tuple absent makes this false.
> ...
Date: Sat, 31 Oct 2009 04:41:14 GMT
Message-ID: <KdPGm.49955$Db2.33801_at_edtnps83>
compdb_at_hotmail.com wrote:
> On Oct 28, 12:51 pm, paul c <toledobythe..._at_oohay.ac> wrote:
...
>> "Each row of the join represents a >> conjunction of propositions, one for each operand"
>
> This doesn't make sense. Perhaps "one from each operand"?
> If so, yes. The predicate associated with r JOIN s is
> (predicate associated with r) AND (predicate associated with s).
> So each result tuple present makes this true and
> each result tuple absent makes this false.
> ...
I was quoting Mr. Scott. Regardless, I don't agree with either interpretation. I realize that many, perhaps most, people who have been trained in logic or read about it would place my attitude somewhere between unfaithful and ignorant, but I would never try to tell a user that some predicates are conjunctions and some aren't. Received on Sat Oct 31 2009 - 05:41:14 CET