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Performance question [message #411834] Tue, 07 July 2009 02:00 Go to next message
Olivia
Messages: 519
Registered: June 2008
Senior Member
WHERE B.k1 = D.k1
AND D.k2 = E.K3
AND E.eff_date >= A.eff_date

In this case, table E joins to both table D and table A, however the join to table A is a range operator (>=). It may seem obvious that table E should be joined after table D, but this is exactly the sort of case where Oracle can mess up.

Why?
Re: Performance question [message #411850 is a reply to message #411834] Tue, 07 July 2009 02:42 Go to previous messageGo to next message
Michel Cadot
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Registered: March 2007
Location: Nanterre, France, http://...
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Why what?

Regards
Michel
Re: Performance question [message #412039 is a reply to message #411834] Tue, 07 July 2009 08:52 Go to previous messageGo to next message
JRowbottom
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Registered: June 2006
Location: Sunny North Yorkshire, ho...
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That's why up to date statistics are important.
Re: Performance question [message #412530 is a reply to message #411834] Thu, 09 July 2009 15:40 Go to previous message
coleing
Messages: 213
Registered: February 2008
Senior Member
Update your STATS first(especially histogram data on this kind of situation) - maybe even delete existing stats and re-gather.

Sometimes Oracle can still get it wrong though - in which case you can look at the ORDERED hint to help you out.
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