Set of solved exercises in Normalization / Normalization Solved Examples / How to find candidate keys, and primary keys in database? / Sets of examples to find the keys of a tables / Process of Key finding in a database – Examples.
- The closure of B, (B)+ = BC from ≠ ABCD. Hence B is not a key. [Refer, How tofind closure/how to find key, purpose of finding attribute closure]
- The closure of D, (D)+ = DA ≠ ABCD. Hence D is not a key. [Refer, How to find closure/how to find key, purpose of finding attribute closure]
- The closure of B and D together, i.e., (BD)+ = ABCD. All the attributes can be determined. Hence, BD is a key (a composite key).
Go back to Normalization - solved exercises page.