Think of it as one line in a WHERE clause.
--
Jonathan Lewis
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Author of:
Practical Oracle 8i: Building Efficient Databases
Ryan Gaffuri wrote in message ...
>Ive been reading the OTN performance tuning guide. I dont really understand
>this paragraph.
>
>What is meant by predicate?
>
>"It is possible for the DBA to generate statistics that quantify the data
>distribution and storage characteristics of tables, columns, indexes, and
>partitions. The cost-based optimization approach uses these statistics to
>calculate the selectivity of predicates and to estimate the cost of each
>execution plan. Selectivity is the fraction of rows in a table that the SQL
>statement's predicate chooses. The optimizer uses the selectivity of a
>predicate to estimate the cost of a particular access method and to
>determine the optimal join order."
>
>
Received on Fri Mar 15 2002 - 02:18:01 CST
