Date: Sun, 01 Jun 2008 15:36:20 GMT
Brian Selzer wrote:
> "paul c" <toledobysea_at_ac.ooyah> wrote in message
>> 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 - 17:36:20 CEST