Q11,paper2,d13 The student marks should not be greater than 100. This is

(A) Integrity constraint

(B) Referential constraint

(C) Over-defined constraint

(D) Feasible constrain.

Answer A.

Constraints are the conditions that must be satisfied by all the tuples of the relation. The types of constraints are as follows.

·         Key constraints

·         Entity integrity constraints

·         Referential integrity constraints

Key constraint tells that there should be a key to identify the unique tuple.

Entity intity constraints tells that primary key value cannot be null.

Referential integrity rule 2 says that a foreign key  in table A refers to the primary key of B. Then every value of foreign key in table A must be null or be available in table B.

Where as some constraints are given by DBA to maintain the quality of data. Like

Create table abc( name varchar (20), marks integer check marks<=100),

It will not allow to insert marks grater than 100..