December 2002
Intermediate to advanced
928 pages
85h 29m
English
Hints can be used to direct the Oracle query optimizer to use a specific optimization technique for a query.
Hints are embedded as comments in a SQL query, with the following syntax:
sql_action/*+hint*/
or
sql_action--+hint
where sql_action is a SELECT, INSERT, UPDATE, or DELETE statement. The hint can also include a text comment for documentation purposes. Any statement can have multiple hints. If a hint is incorrect or invalid, Oracle ignores the hint without causing an error.
The following sections describe hints in a variety of categories: optimizer mode hints, access path hints, query transformation hints, join hints, parallel execution hints, and miscellaneous hints.