Re: How to do a difference on two sets from same table?
Date: Tue, 31 Aug 2004 10:38:51 -0400
Message-ID: <2IadnZOYKbBuEancRVn-rw_at_comcast.com>
"Alan" <not.me_at_uhuh.rcn.com> wrote in message
news:2eSYc.10965$Tq.9705_at_trndny02...
> FROM same_place
As usual, your comments are excellent.
I do have a quibble with you on this one. The "FROM same_place" is
When the sets are both drawn from the same source, it's possbile to express
> WHERE other_condition
to draw the second set from the same source as the first, just as you don't
necessarily have to draw both sets
from the same source in UNION.
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.
Received on Tue Aug 31 2004 - 16:38:51 CEST