Oh, Oracle KNOWS that "where 1=2" is always false, so it knows that the
resultset will be empty. But it has to come up with a plan, so I assume it
just takes the simplest plan it knows - a full table scan - knowing full
well that it does not actually have to do the scan.
At 05:58 PM 4/3/2003 -0800, you wrote:
>I'm going to take a guess, since I know that there is at least one member
>of the list that can do better, but here goes...
>
>Predicates (where clauses) are applied as result sets are processed.
>Oracle has no knowledge that the predicate will always evaluate to false.
>This results in a row being read, checking the predicate and rejecting the row.
>
>Okay, gurus, please correct me if I am wrong (by the way, I'm being
>totally serious...)
Wolfgang Breitling
Centrex Consulting Corporation
http://www.centrexcc.com
********************
This email communication is intended as a private communication for the sole use of the primary addressee and those individuals listed for copies in the original message. The information contained in this email is private and confidential and if you are not an intended recipient you are hereby notified that copying, forwarding or other dissemination or distribution of this communication by any means is prohibited. If you are not specifically authorized to receive this email and if you believe that you received it in error please notify the original sender immediately. We honour similar requests relating to the privacy of email communications.
Cette communication par courrier électronique est une communication privée à l'usage exclusif du destinataire principal ainsi que des personnes dont les noms figurent en copie. Les renseignements contenus dans ce courriel sont confidentiels et si vous n'êtes pas le destinataire prévu, vous êtes avisé, par les présentes que toute reproduction, tout transfert ou toute autre forme de diffusion de cette communication par quelque moyen que ce soit est interdit. Si vous n'êtes pas spécifiquement autorisé à recevoir ce courriel ou si vous croyez l'avoir reçu par erreur, veuillez en aviser l'expéditeur original immédiatement. Nous respectons les demandes similaires qui touchent la confidentialité des communications par courrier électronique.
