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2015-k-db-jonathan_lewis-five_hints_for_optimising_sql-praesentation
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Five Hints for Optimal SQL
Jonathan Lewis
jonathanlewis.wordpress.com
www.jlcomp.demon.co.uk
Five hints
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Jonathan Lewis
© 2008 - 2015
Who am I ?
Independent Consultant
32+ years in IT
27+ using Oracle
Strategy, Design, Review,
Briefings, Educational,
Trouble-shooting
Oracle author of the year 2006
Select Editor’s choice 2007
UKOUG Inspiring Presenter 2011
ODTUG 2012 Best Presenter (d/b)
UKOUG Inspiring Presenter 2012
UKOUG Lifetime Award (IPA) 2013
Member of the Oak Table Network
Oracle ACE Director
O1 visa for USA
2
Five hints
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Jonathan Lewis
© 2008 - 2015
The Problem
"Left-deep"
Bad choice of transformation
Restrictions on transformations
Bad Estimates
Bad join order
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Jonathan Lewis
© 2008 - 2015
Left-deep tree
The optimizer’s strategy is always to work towards a ‘left-deep’ tree. We
traverse the tree from the bottom left corner going across then up.
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