- A hint is an instruction to the optimizer which can influence the optimizer to choose a difference plan for a sql statement. The optimizer uses these hints to choose an execution plan for the statement.
- Hints should be used only as LAST RESORT if statistics were gathered properly and query is still following a sub-optimal execution plan.
DBAs and developers use below hints in their day-to-day tuning
1. INDEX
2. ORDERED
3. PARALLEL
4. FIRST_ROWS
5. FULL
6. LEADING
7. USE_NL
8. APPEND
9. USE_HASH
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