Q83
Which three tasks are handled by the optimizer?
A. Decide which indexes to use.
B. Rewrite the WHERE clause.
C. Parse the query.
D. Change the order in which the tables are joined.
E. Validate the query.
F. Execute the query.
G. Verify that the user is allowed to execute the query.
解析:
优化器会(1)重写where条件(2)决定使用哪个索引(3)决定连接表的顺序
参考资料:https://dev.mysql.com/doc/refman/5.7/en/where-optimization.html
选择 ABD
Answer: B,C,F