Query block hints operate on single query blocks. Note that USE_NL (table1 table2) is not considered a multi-table hint because it is actually a shortcut for USE_NL(table1) and USE_NL(table2). LEADING is an example of a multi-table hint. Multi-table hints are like single-table hints, except that the hint can specify one or more tables or views. INDEX and USE_NL are examples of single-table hints. Single-table hints are specified on one table or view. Hints falls into the following general classifications: Oracle Enterprise Manager Concepts for information on monitoring and tuning with Oracle Enterprise Manager features.Chapter 6, "Automatic Performance Diagnostics" for information on analyzing and tuning SQL statements.Hints for Optimization Approaches and Goals. The hints are grouped into the following categories: See "Using Optimizer Hints" for the discussion of the types and usage of hints. In such a case, use hints to force the optimizer to use the optimal execution plan. Based on this information, you might be able to choose a more efficient execution plan than the optimizer. Hints provide a mechanism to direct the optimizer to choose a certain query execution plan based on the specific criteria.įor example, you might know that a certain index is more selective for certain queries. As an application designer, you might know information about your data that the optimizer does not know. Hints let you make decisions usually made by the optimizer. The chapter contains the following sections: This chapter explains how to use hints to force various approaches. Optimizer hints can be used with SQL statements to alter execution plans.
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