aa8d7cd2_Cost_Based_Oracle_Fundamentals__Comments
[Chapter] Chapter 9 [Last addendum] 24th March 2006 [Title] Query Transformation [Comments] 
Before the optimizer starts to do arithmetic, it may restructure your query in a variety of ways. This restructuring is generally known as query transformation. This chapter describes a few of those transformations – and then points out that one of the enhancements in 10g means that the optimizer might actually do several sets of arithmetic with a single query: some before, and some after transforming your query.
Cost Based Oracle Fundamentals
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