Re: Order in Where Clause

Ron,

Depending upon the selectivity of your where predicates, you can improve or hurt your response time by reordering them. Oracle evaluates predicates as it does table names in the FROM clause - backwards - that is, bottum up. Therefore, you should strive to put the MOST restrictive predicates LAST in your list of predicates.

Steve Helle
helle_at_ksr.com

Ron A. Olshavsky (rono_at_netcom.com) wrote:
: Can anyone give a decent answer to how thigs should be ordered in a WHERE
: clause of a lrage multi-table select?
 

: Ive heard it matters a great deal, to it doesnt matter at all...
 

: I know that the FROM is very important, and simply chaing the order the
: tables are listed in cut a large query time in half...
 

: Can optimizing the WHERE statement help anymore?
 

: Ron
: --
: ,,,
: (o o)
: +------------------------------oOO--(_)--OOo--------------------------------+
: | | It's a Mr. Death or something, |
: | Ron A. Olshavsky - rono_at_netcom.com | He's come about the reaping? |
: | | I dont think we need any... MP:MOL |
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Received on Mon Jul 25 1994 - 18:40:33 CEST