Re: Guessing?

From: paul c <toledobysea_at_ac.ooyah>
Date: Sun, 01 Jun 2008 15:36:20 GMT
Message-ID: <Ulz0k.25$i01.23@pd7urf2no>


Brian Selzer wrote:
> "paul c" <toledobysea_at_ac.ooyah> wrote in message
> news:sfm0k.179265$rd2.156266_at_pd7urf3no...
...

>> When the relations in a union view expression are union-compatible 
>> (so-called), I wish somebody could show me how any disjunction is involed 
>> in the tuples of the union view.   Many people say that the predicate must 
>> be disjunctive, but I'd say that the machinery of the RM has completely 
>> discounted that.

>
> I don't see how that could be. If you start out with two base relations
> with the same heading, then each of those relations has its own distinct
> predicate. The predicate of a view that is the result of the union of the
> two base relations is obviously just a disjunction of the predicates of the
> base relations, and each tuple in the view originated from either or both of
> the base relations, and thus satisfies at least one but possibly both of the
> predicates of the base relations.
>

I'd say you are not alone. However, take the union of two base relations and assign it to another base relation (as opposed to a view).   Would you say the predicate of the result is also disjunctive? Received on Sun Jun 01 2008 - 10:36:20 CDT

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