A user with clearance C cannot insert a tuple (CR74, “David”, “Sinclaire”) into the Clientrelation because it violates the primary key constraint.
However, this inability to insert the new tuple with clientNo=“CR74” compromises the security requirement.
That is, the users with lower security level should not be able to infer any information about objects that have a higher security classification.
A user with clearance “C” should NOT be able to know that there exists a tuple with security level “S” contains a client No=“CR74”
How to fix this problem –set the security Classas a part of the primary key of the Client relation –(security Class, client No)