Question

Which of the following is not a condition for X→  Y in Boyce codd normal form?

(a) X →  Y is trivial

(b) X is the superkey for the relational schema R

(c) Y is the superkey for the relational schema R

(d) All of the mentioned

The question was asked in examination.

This intriguing question comes from Decomposition Using Functional Dependencies topic in portion Relational Database Design of RDBMS

Answer 1

Right option is (c) Y is the superkey for the relational schema R

Easiest explanation: Y does not need to be a superkey of the relation for the given functional dependency to satisfy BCNF. X→ Y must be trivial and X must be the superkey of the relation R.