FUNCTIONAL DEPENDENCIES & ARMSTRONG'S AXIOMS
Redundancy in relation may cause insertion, deletion and updation anomalies Normalization is the process of minimizing redundancy from a relation or set of relations . I t helps to minimize the redun dancy in relations , hence avoids anomalies . A functional dependency (FD) for relation R is a formula of the form A à B where A and B are sets of attributes of R. We say A functionally determines the B , or B is functionally dependent on the A . Trivial functional dependency : A → B has trivial functional dependency if B is a subset of A . Non Trivial Functional Dependency : If a functional dependency X->Y holds , where Y is not a subset of X then this dependency is called non trivial Functional dependency . Multi valued dependency : occurs when two attributes in a table are independent of each other but, both depend on a third attribute . Transitive dependency: functional dependency is said to b...