Examine the following statement that is used to modify the primary key constraint on the SALES tabl

Examine the following statement that is used to modify the primary key constraint on theSALES table:SQL> ALTER TABLE SALES MODIFY CONSTRAINT pk DISABLE VALIDATE;Which three statements are true regarding the above command? (Choose three.)选项A.The constraint remains valid.B.The index on the constraint is dropped.C.It allows the loading of data into the table using SQL *Loader.D.New data conforms to the constraint, but existing data is not checked.E.It allows the data manipulation on the table using INSERT/UPDATE/DELETE SQL statements.

Correct Answers: A B

【考点分析】约束的DISABLE VALIDATE属性 

【题意简述】把表的主键约束修改为DISABLE VALIDATE,描述正确的是?

【答案剖析】. 

A: 正确, DISABLE VALIDATE的约束是有效的 

B: 正确,主键约束会自动维护一个唯一性索引,约束enable,索引在,disable,索引不在

C: 错误, DISABLE VALIDATE不允许做DML操作,无法导入数据 

D: 错误, DISABLE VALIDATE的约束对已有数据校验,新数据不校验,说反了 E: 错误,不允许做INSERT/UPDATE/DELETE DML操作