Oracle-L: RE: Sequential Tables' Selects Versus Joins

From: Jeff Holt <jeff.holt_at_hotsos.com>
Date: Wed, 28 Aug 2002 09:08:25 -0800
Message-ID: <F001.004C19DE.20020828090825@fatcity.com>

If it appears as though this might perform better than a single query, then it's probably because the existing query's execution plan is sub-optimal. Fix it and forget about splitting it up. If you feel compelled to split it up, then consider that act as an exercise in learning how to optimize SQL execution plans. The act of splitting it up will probably reveal one of two things:

The query's semantics aren't selective enough to make any plan acceptable (either because of the number of blocks and rows that must be visited or because of the design of the schema).
There is a more optimal execution plan for the statement if you alter the schema, fiddle with the text of the statement, or possible change a global parameter (yikes).

Jeff Holt
Hotsos Enterprises, Ltd.
http://www.hotsos.com

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-----Original Message-----
VIVEK_SHARMA
Sent: Wed, Aug 28, 2002 10:33
To: Multiple recipients of list ORACLE-L

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

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Author: VIVEK_SHARMA
INET: VIVEK_SHARMA_at_infosys.com

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Author: Jeff Holt
INET: jeff.holt_at_hotsos.com

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