Re: Aggregates and associated relational operators

"Mikito Harakiri" <mikharakiri_at_ywho.com> wrote in message news:6Z86b.35$pP2.199_at_news.oracle.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:oK96b.557$Lp.53402758_at_mantis.golden.net...
> > "Mikito Harakiri" <mikharakiri_at_ywho.com> wrote in message
> > news:ry86b.30$pP2.101_at_news.oracle.com...
> > > Some time ago there has been already a small thread about broken
> symmetry
> > > among relational operators ("Naisetrac Product", which BTW should
> properly
> > > called "Tensor Product"). Recent discussion about "fundamental"
> aggregates
> > > satisfying identities like this:
> > >
> > > sum(a union b) = sum(a) + sum(b)
> >
> > Am I missing something? I don't recall anyone suggesting the above
> identity,
> > and it seems to me the identity would be:
> >
> > sum(a union b) = sum(a) + sum(b) - sum(a intersect b)
> >
> > Are you using multiset union?
> >
> >
> > > max(a union b) = max(max(a),max(b))
> >
> >
> > > prompts a related question:
> > > Why union operator is so special that it has associated aggregation?
Is
> > > there anything similar to aggregation that is missing?
> >
> > I do not understand the questions. Could you clarify them a little?
>
> Agreed. With your correction, if I use sets, then the aggregate identity
is
> no longer similar among different aggregates, nor it makes "union"
special.
> I also understand that multisets wouldn't be interested to at least part
of
> the audience:-(

They are still interesting to some. Can you clarify the two questions a little? Received on Sat Sep 06 2003 - 02:24:25 CEST