Re: more on delete from join

From: Mr. Scott <>
Date: Fri, 28 Aug 2009 13:32:36 -0400
Message-ID: <>

"paul c" <> wrote in message news:WFTlm.41198$Db2.23941_at_edtnps83...
> Mr. Scott wrote:

>> "paul c" <> 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

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