hi
Firstly, can we please keep this online?
My opinion (observation!)..
in RBO the driving table is the rightmost
in CBO it need not be so..cos the optimizer
decides the order.
can someone confirm the observation regarding
CBO?
Thanx
PS: sorry If i missed this...in some earlier post.
But can someope please explain to me
how Oracle processes
EXISTS/NOT EXISTS and IN/NOT IN
I have read (been told and also observed)
that EXISTS/NOT EXISTS
performs better than IN/NOT IN, but have always
wondered HOW
------------- Original Message --------------
[EMAIL PROTECTED] wrote:
To:Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
From:[EMAIL PROTECTED]
Date:Fri, 06 Apr 2001 10:18:00 -0800
Subject:Re:Driving table
Anup,
This can get into a lengthy discussion, but I'll try to keep it short. In
general you can use this in both CBO and RBO, since in my experience doing
things well for RBO has no ill affect on CBO.
The table order in the 'from' clause should match the order in the 'where'
clause. Since Oracle reads a statement backwards, bottom to top, left to right,
the last table listed in the 'from' clause should have the most restrictive and
therefore the last condition in the 'where' clause. The reason for caring about
the driving table is that the rows returned from that table drive the remainder
of the query. So if you can return the least number of rows from that table you
then have less work to do thereafter.
If you want a more detailed discussion, can we take it off-line.
Dick Goulet
____________________Reply Separator____________________
Author: [EMAIL PROTECTED]
Date: 4/6/2001 2:45 AM
Hi friends ,
I have got some query regarding , how the query is exactly executed ??
We always take joins and if we see the plan of the query , there is always one
main driving table . Some times I get feeling that , in the join the right
most table is the driving table . But that is not always true , this is my
observation from several plans .
In Oracle documentation alos ita mentioned that ( Server Concepts, 815 or 816
: Optimisation of Joins ), "one driving table is selected" , but at least I
cannot makeout which of the several tables will be selected as driving table .
What can be the potential criterions of selecting a driving table ?
Please , if you all can throw some light on the same or can redirect to some
document , that would be great .
Cheers ,
Anup Saxena
-------------------------------------------------------------------
The contents of this e-mail are confidential to the ordinary user
of the e-mail address to which it was addressed and may also be
privileged. If you are not the addressee of this e-mail you should
not copy, forward, disclose or otherwise use it or any part of it
in any form whatsoever. If you have received this e-mail in error
please notify us by telephone or e-mail the sender by replying to
this message, and then delete this e-mail and other copies of it
from your computer system. Thank you.
We reserve the right to monitor all e-mail communications through
our network.
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author:
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author:
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
_____________________________________________________
Chat with your friends as soon as they come online. Get Rediff Bol at
http://bol.rediff.com
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Cyril Thankappan
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
