OCP-1Z0-051-V9.02-46题

biao199423

46. Which statements are correct regarding indexes? (Choose all that apply.)A. When a table is dropped, the corresponding indexes are automatically dropped. B. A FOREIGN KEY constraint on a column in a table automatically creates a nonunique index.C. A nondeferrable PRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a uniqueindex.D. For each data manipulation language (DML) operation performed, the corresponding indexes areautomatically updated. Answer: ACD答案解析：参考：http://blog.iyunv.com/rlhua/article/details/12780775A正确，在删除表时，会删除相应的索引。B错误，外键不能够自动创建索引，只有主键约束和唯一性约束才能自动创建唯一的索引。C正确，在表定义中定义了PRIMARY KEY 或UNIQUE 约束条件，则会自动创建一个唯一的索引。D正确，在具有索引的表上提交每项DML 操作后，都意味着必须更新相应的索引。


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