Re: Curious SQL question

"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message news:3INnh.41260$cz.607000_at_ursa-nb00s0.nbnet.nb.ca...
> J M Davitt wrote:
> > Neo wrote:
> >
> >>> select distinct orders.customer_id, products.product_id
> >>> from orders, products
> >>> minus
> >>> select distinct customer_id, product_id
> >>> from products;
> >>>
> >>> The first select esablishes a "universe of discourse" for the query
by
> >>> joining every customer with every product. The second select excludes
> >>> products that a customer did buy.
> >>
> >>
> >>
> >> The above SQL makes the solution easy to understand (should the last
> >> line of the SQL be orders instead of products). Assuming the following:
> >>
> >> set A = {shampoo, soap, bread, wine}
> >> set B = {shampoo, soap, bread}
> >> set C = {wine}
> >>
> >> What is the most appropriate name of the function that does the
> >> following:
> >>
> >> C = f (A, B);
> >>
> >> Is it NAND, NOT INTERSECTION, NOT IN? And should the order of the
> >> inputs (A, B) matter?
> >>
> >
> > Uh, isn't that 'A MINUS B' or, if you prefer, MINUS (A, B).
>
> What about XOR(A,B) ?

Read Marshall's response, concerning "symmetric difference".

XOR is commutative. MINUS is not. Unless I'm misreading something. Received on Sat Jan 06 2007 - 15:20:16 CET