aa8d7cd2_Cost_Based_Oracle_Fundamentals__Comments
[Chapter] Chapter 7 [Last addendum] 13th Sept 2012 [Title] Histograms [Comments] 
There are good reasons for creating histograms on a few columns in the database. Unfortunately, the commonest reason quoted for creating them is not the best reason for creating them. Histograms can help the optimizer handle some of the situations where the normal selectivity calculations go wrong – it’s much more subtle than just choosing between indexes and tablescans.
Cost Based Oracle Fundamentals
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