Re: How to do a difference on two sets from same table?
From: Dan <dan_at_nospam.com>
Date: Tue, 31 Aug 2004 13:20:16 -0500
Message-ID: <qj3Zc.17$Wz4.43636_at_news.uswest.net>
>>necessarily have to draw both sets
>>from the same source in UNION.
>>
>>When the sets are both drawn from the same source, it's possbile to
>>the result without a MINUS,
>>by just saying WHERE some_condition AND NOT other_condition. This leaves
>>the learner in a quandary about
>>why the MINUS had to be added to the already complex bag of things to be
>>learned. The MINUS is more useful,
>>and sometimes necessary, when the two sets are drawn from different
>>sources. The same comment applies to UNION.
>>
>>
>>
Date: Tue, 31 Aug 2004 13:20:16 -0500
Message-ID: <qj3Zc.17$Wz4.43636_at_news.uswest.net>
On 8/31/2004 12:02 PM, Alan wrote:
> "Laconic2" <laconic2_at_comcast.net> wrote in message
> news: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
>>>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
> > don't >
>>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
> > express >
>>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. > >
Dan Received on Tue Aug 31 2004 - 20:20:16 CEST