Which constraint can be defined only at the column level?
A.
UNIQUE
B.
NOT NULL
C.
CHECK
D.
PRIMARY KEY
E.
FOREIGN KEY
Explanation:
the NOT NULL constraint can be specified only at the column level, not at the table level.
Incorrect answer:
AUNIQUE can be define at table level
CCHECK can be define at table level
DPRIMARY KEY can be define at table level
EFOREIGN KEY can be define at table level
Refer: Introduction to Oracle9i: SQL, Oracle University Study Guide, 10-8
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