Re: more on delete from join
Date: Fri, 28 Aug 2009 13:32:36 -0400
"paul c" <toledobythesea_at_oohay.ac> wrote in message
> Mr. Scott wrote:
>> "paul c" <toledobythesea_at_oohay.ac> wrote in message >> news:eimlm.40861$Db2.21494_at_edtnps83...
>>> I don't know if the plural 'disjunctions' is a typo'. Do you mean that >>> the resulting value of R stands for "r1 OR r2, etc." is true? >> >> I don't seem to be getting through. >> >> AND is to INTERSECTION as OR is to UNION. >> ,,, >
> That's a stretch, it would be more accurate to say that <AND> is to
> relational intersection as <OR> is to relational union. If what you wrote
> is what most people think it might help explain why so many want to
> associate the result of a relational operation with the operations used
> for form the result, even though the form of the resulting set of tuples
> offers no way to record the operations that were used to produce it.
> I think it is kind of phony for people to appeal at all to algebraic
> operations in this way when the strict use of algebra can use <OR> to
> produce a relation that is algebraically equal to one produced by <AND>.
> That's why I sometimes say a union is always a join, even though it does
> seem to wind people up. The expression used to form a view can be said to
> persist only if it is recorded as a constraint, which I would say it
> should be.
I give up. Instead of applying plain old ordinary logic, you appear to have strange preconceived notions that are a mystery to me. Without a common frame of reference, there's no point in continuing this discussion. Received on Fri Aug 28 2009 - 19:32:36 CEST