多项选择题

A. It automatically performs verification or evolves no……

Which three statements are true about adaptive SQL plan management?（）

A. It automatically performs verification or evolves non-accepted plans, in COMPREHENSIVE mode when they perform better than existing accepted plans.
B. The optimizer always uses the fixed plan, if the fixed plan exists in the plan baseline.
C. It adds new, bettor plans automatically as fixed plans to the baseline.
D. The non-accepted plans are automatically accepted and become usable by the optimizer if they perform better than the existing accepted plans.
E. The non-accepted plans in a SQL plan baseline are automatically evolved, in COMPREHENSIVE mode, during the nightly maintenance window and a persistent verification report is generated.

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单项选择题Examine the parameter for your database instance: You generated the execution plan for the following query in the plan table and noticed that the nested loop join was done. After actual execution of the query, you notice that the hash join was done in the execution plan: Identify the reason why the optimizer chose different execution plans.（）

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