December 2002
Intermediate to advanced
928 pages
85h 29m
English
To improve the optimization of SQL statements, Oracle introduced the cost-based optimizer in Oracle7. As the name implies, the cost-based optimizer does more than simply look at a set of optimization rules. It selects the execution path that requires the least number of logical I/O operations and thus the lowest cost for the completion of the query. This approach avoids the potential problems discussed in the previous section.
Oracle8 and later versions will use the cost-based optimizer to identify the optimal execution plan if any statistics for any table or index are present.