Re: Fav. Urban Legend...

In that same vein, ( or is it vane, or maybe even vain? ;) I tried removing a correlated subquery from a bit of SQL just yesterday.

It was duly replaced with an inline view, and the time to run the query increased by %20. :)

Jared

On Saturday 16 March 2002 01:53, Jonathan Lewis wrote:
> 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
> http://www.jlcomp.demon.co.uk/seminar.html
>
> Host to The Co-Operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
> Author of:
> Practical Oracle 8i: Building Efficient Databases
>
>
> -----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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