Oracle Certification Interview Question:

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

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B. A columns with the UNIQUE constraint can contain NULL values
D. A constraint can be disabled even if the constraint column contains data
Submitted by: Administrator