⟩ Explain Which two statements are true regarding constraints? (Choose two.) A. A foreign key cannot contain NULL values B. A columns with the UNIQUE constraint can contain NULL values C. A constraint is enforced only for the INSERT operation on a table D. A constraint can be disabled even if the constraint column contains data E. All constraints can be defined at the column level as well as the table level
B. A columns with the UNIQUE constraint can contain NULL values
D. A constraint can be disabled even if the constraint column contains data