Re: How to do a difference on two sets from same table?
Date: Tue, 31 Aug 2004 13:02:47 -0400
"Laconic2" <laconic2_at_comcast.net> wrote in message
> "Alan" <not.me_at_uhuh.rcn.com> wrote in message
> > FROM same_place
> > WHERE other_condition
> As usual, your comments are excellent.
> I do have a quibble with you on this one. The "FROM same_place" is
> misleading. You don't always have
> to draw the second set from the same source as the first, just as you
> necessarily have to draw both sets
> from the same source in UNION.
> When the sets are both drawn from the same source, it's possbile to
> the result without a MINUS,
> by just saying WHERE some_condition AND NOT other_condition. This leaves
> the learner in a quandary about
> why the MINUS had to be added to the already complex bag of things to be
> learned. The MINUS is more useful,
> and sometimes necessary, when the two sets are drawn from different
> sources. The same comment applies to UNION.
I agree- I was debating whether or not to get into it- but I decided just to give a very simple (unintimidating) example. I am surprised that Brio doesn't offer MINUS. It could be that there is an end-user version and a developer's version. I've seen this with several other tools. Received on Tue Aug 31 2004 - 19:02:47 CEST