Which syntax turns an existing constraint on?
ALTER TABLE table_name ENABLE constraint_name;
ALTER TABLE table_name STATUS = ENABLE CONSTRAINT constraint _ name;
ALTER TABLE table_name ENABLE CONSTRAINT constraint _ name;
ALTER TABLE table_name TURN ON CONSTRAINT constraint _ name;
To turn on an existing constraint, option C is correct:
The correct syntax to turn on an existing constraint is:
C. ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;
Option A is also a valid syntax for enabling a constraint.
Option B is incorrect because there is no "STATUS" option for the ALTER TABLE statement.
Option D is incorrect because there is no "TURN ON" option for the ALTER TABLE statement.
Therefore, the answer is: C. ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;