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Message Posted: Fri, 07 May 2004 @ 21:28:31 GMT

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The following statement is 100% not true.:

     -----Original Message Start-----
     From: Clark, Lisa
     Sent: Friday, May 07, 2004 14:04
     Subject: Re: Parallelism vs. Oracle

     A HINT in Oracle is a suggestion to the optimizer - you cannot force
     a change to the execution plan.
     -----Original Message End-----

If the syntax of your hint is correct the Oracle execution plan _will_ be changed. For example queries that select from large tables without collected statistics will frequently use nested loop joins; the USE_HASH hint you'll force the Oracle engine to perform the more efficient in this case hash join. In similar way you can force parallel execution, the order of table joins, to use or not particular index, star- transformation etc. However if the hint syntax is incorrect then it will be ignored without any error.

For a brief example on Oracle hints check

www.cisnet.baruch.cuny.edu/holowczak/classes/9440/queryprocessing/sql_example/

while for the full details download the SQL documentation from

www.otn.oracle.com/documentation/database10g.html

Rgds,

Dr. Alex Haralampiev, M.Eng, CNA, OCP, TCP
Database Architect
Nationwide Financial

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