A PRIMARY KEY constraint can be added to an existing table by using the ____ clause of the ALTER TABLE command.
A) MODIFY
B) ADD
C) CONSTRAINT
D) none of the above

Question

A PRIMARY KEY constraint can be added to an existing table by using the ____ clause of the ALTER TABLE command.​
A) ​MODIFY
B) ​ADD
C) ​CONSTRAINT
D) ​none of the above

Quizplus · Accepted Answer

To add a PRIMARY KEY constraint to an existing table, we use the ADD clause of the ALTER TABLE command. We specify the column(s) that will be part of the primary key as well as the PRIMARY KEY keyword. For example: ALTER TABLE my_table ADD PRIMARY KEY (column1, column2);

A PRIMARY KEY Constraint Can Be Added to an Existing