75、Which statements are correct regarding indexes? (Choose all that apply.)

A. A non-deferrable PRIMARY KEYor UNIQUE KEYconstraint in a table automatically attempts to creates a unique index.

B. Indexes should be created on columns that are frequently referenced as part of any expression.

C. When a table is dropped, the corresponding indexes are automatically dropped.

D. For each DML operation performed, the corresponding indexes are automatically updated.

Correct Answer: ACD

Section: (none)

Explanation：解析，有点数据库管理的意思