“…Optimizer doesn't need to identify the optimal plan for the query on creating a query plan for various reasons. Hints apply only to the optimization of the block of a statement in which they appear [11]. A statement block is any one of the following statements or parts of statements: A simple SELECT, UPDATE, or DELETE statement A parent statement or subquery of a complex statement A part of a compound query If a compound query consisting of two component queries combined by the UNION operator has two blocks, one for each component query, then hints in the first component query apply only to its optimization, not to the optimization of the second component query.…”