RE: Help - Tuning SQL

Regarding the first point the easiest way to check is to run explain plan fro the 2 statements and compare the results On the second point the != issue
Guy Harrisons's excellent book Oracle SQL - High Performance Tuning states "Oracle will not employ an index if the NOT EQUALS operator is employed."

Using > and < will use an index (other conditions permitting)

HTH John

-----Original Message-----
Michael A
Sent: 28 February 2001 19:51
To: Multiple recipients of list ORACLE-L

I've got some simple questions on tuning SQL. Please reply with references, I'm not looking for guesses.

• If you have a SELECT statement with a WHERE clause and 2 AND clauses, which one is processed first, the WHERE clause, the first AND clause, or the second AND clause?
• Is there any performance loss in using "<>" over "!="?

Michael Armstead
Database Administrator, OCP-Certified
Corporate & Finance Information Systems
Glaxo SmithKline

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