C H A P T E R  14

Implementing Query Hints

Placing hints in SQL is a common and simple approach to improve performance. Hints influence Oracle's optimizer to take a specific path to accomplish a given task, overriding the default path the optimizer may have chosen. Hints can also be viewed as a double-edged sword. If not implemented and maintained properly, they can hurt performance in the long run.

The most popular reason to use hints is simply to get data out of the database faster, and many of the available hints are geared for that purpose. The Oracle database supports more than 60 hints, so it is apparent that hints can be placed in SQL for a multitude of reasons. The purpose of this chapter is to categorize these hints into subsets, and ...

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