Re: Fav. Urban Legend...

On that line, I've just had a note from Gaja about my commentary on the line:

    "Rewrite all correlated subqueries using in-line views".

He was concerned that I may not think the advice valid. So let me say quite categorically that the comment was not a criticism of the technique.

Converting a subquery into a join is a strategy which will very often result in significant performance benefits and Gaja is, I think, the first person I have seen make a very special mention of it in a public paper. (No doubt someone will correct me on that quite soon).

My point was that although it is not the automatic, the only, or even necessarily the correct solution to the sight of a correlated subquery, Gaja's paper will, one day, be quoted as the definitive proof that you should ALWAYS do it. And such is the stuff of the urban legend.

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Next Seminar - UK, April 3rd - 5th
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-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 16 March 2002 09:27

|
|You're cheating. Most advice containing 'always', even only once,
stands
|a big chance of becoming a legend very soon.
|--
|Regards,
|
|Stephane Faroult
|Oriole Ltd

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Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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