Performance Testing Question

From: Ryan Gaffuri <rkg100_at_erols.com>
Date: Thu, 14 Mar 2002 22:43:22 -0400
Message-ID: <a6rqlt$q8n$1@bob.news.rcn.net>

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 Thu Mar 14 2002 - 20:43:22 CST