Define the Boyce-Codd Normal Form with instance and also Compare BCNF and 3NF.

 Ans: BCNF: For each functional dependency X->Y in a set F of functional dependencies over relation R, either: 

• Y is a subset of X or,
• X is a superkey of R

 While

3NF: For each functional dependency X->Y in a set F of functional dependencies over relation R, either:  

• Y is a subset of X or,
• X is a superkey of R, or
• Y is a subset of K for few key K of R

a.       there is no subset of a key is a key