Optimizer Directives That Are Embedded in Queries

Optimizer directives are comments in a SELECT statement that instruct the query optimizer how to execute a query. You can also place directives in UPDATE and DELETE statements, instructing the optimizer how to access the data. Optimizer directives can either be explicit directions (for example, use this index or access this table first), or they can eliminate possible query plans (for example, do not read this table sequentially or do not perform a nested-loop join).