Oracle Certificate Profession 1Z0-051-29

（29）Which two statements are true regarding constraints? (Choose two.)

A. A foreign key cannot contain NULL values.

B. The column with a UNIQUE constraint can store NULLS .

C. A constraint is enforced only for an INSERT operation on a table.

D. You can have more than one column in a table as part of a primary key.

答案：（B、D）

重複：28

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