Re: <OR> predicate?

On Sep 29, 10:22 am, Erwin <e.sm..._at_myonline.be> wrote:
> On 29 sep, 16:40, Vadim Tropashko <vadim..._at_gmail.com> wrote:
>
> > A bulk of discussion is devoted to introduction of PLUS predicate, but
> > then, I fail to see how given the two relations EMP and PLUS one can
> > express the query "give employee departement numbers wit salary
> > totals" in relational algebra, and, therefore in A-algebra.
>
> I think PLUS is of no use to you in this situation.
>
> The function/relation you need to come to the aggregate results is a
> function that maps a relation {1 2 3} (deliberately using sloppy
> shorthand here) onto, e.g. if the aggregation operation is addition,
> the number 6.  The relation that represents the invoked aggregate
> operator (SUM, COUNT, ...) in question, that is.
>
> Or is that not the problem ?

Oh, that route I've explored at sufficient depth: http://vadimtropashko.wordpress.com/relational-programming-with-qbql/aggregation-and-set-joins/ Received on Wed Sep 29 2010 - 20:05:09 CEST