Question

At the time of creation of table X, the database administrator specified Y as the Primary key. Later on he realized that instead of Y the combination of column P and Q should have been the primary key of the table. Based on this scenario, answer the following questions :

(a) Is it possible to keep Y as well as the combination of P and Q as the primary key?

(b) What statement(s) should be entered to change the primary key as per the requirement.

Answer 1

(i) No - A table can have only one primary key.

(ii) ALTER TABLE X DROP PRIMARY KEY

ALTER TABLE X ADD PRIMARY KEY(PQ)