|
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of DeLong, Eric
Sent: Wednesday, July 16, 2008 12:36 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: SQL Help finding missing records
I don't think so..... NOT EXISTS will use an index scan *IF* the fields
referenced in the WHERE of the subquery exist within an index. I would
agree with that statement in the case of the IN predicate....
Eric DeLong
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of vhamberg@xxxxxxxxxxx
Sent: Wednesday, July 16, 2008 10:32 AM
To: RPG programming on the AS400 / iSeries
Subject: RE: SQL Help finding missing records
Caveat emptor!!
Remember that NOT EXISTS, as well as NOT IN, forces a table scan - you
can't tell if something is not there unless you look at everything.
Learned this at the last COMMON, I think.
Now probably and EXCEPTION JOIN can do better, IF you have supporting
indexes.
Regards
Vern
As an Amazon Associate we earn from qualifying purchases.
This mailing list archive is Copyright 1997-2025 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].
Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.