VIVEK_SHARMA wrote:
>
> Which would Perform Better ?
> 1) Having an SQL Query Doing a Join between 6 Tables
>
> 2) Running 1 SQL Query on a Single Table , getting the Output Values in a Cursor
> & passing the Cursor Values as Arguments to the where Clause of a 2nd SQL Query
> Running on a 2nd Table & thus so on ... thereby finally getting the Output from the 6th Table
>
In the first case you give a free-hand to the optimizer, which, for all
its flaws, doesn't do THAT bad a job. In the second one, you force
(forgetting about the cost of additional cursors etc.) nested loops.
Think about it. God knows I have met awful SQL programmers (people I
wouldn't give SELECT 'HELLO WORLD' FROM DUAL to maintain) but assuming
some reasonable knowledge of SQL and no obvious mistake (eg 2 or 3
missing join conditions fixed by a DISTINCT) 1) is the winner, by a
margin which depends on the query and the developer's skills.
Even in the worst case, the join will be easier to fix by somebody who
is knowledgeable.
BTW a join between 6 tables is not, in itself, a monster query. I have
done worse.
--
Regards,
Stephane Faroult
Oriole Software
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
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Author: Stephane Faroult
INET: sfaroult_at_oriole.com
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Received on Wed Aug 28 2002 - 11:52:04 CDT
