BCNF form

Boyce–Codd normal form (or BCNF or 3.5NF) is a normal form used in Database normalization. It is a slightly stronger version of the third normal form (3NF). BCNF was developed in 1975 by Raymond F. Boyce and Edgar F. Codd

It is used to address certain types of anomalies not dealt with by 3NF and increase data integrity by organizing the columns and tables of a relational database in order to achieve database normalization. BCNF Every determinant may be a candidate key and Candidate keys must be unique. 

BCNF hold condition that is−

For any non-trivial functional dependency, B → A, B must be a super-key.

Consider a database table that stores Student information and has the attributes <Student_Id>, <First_name>, <Last_name>, and <Title>.

In this table, the field <Student_Id> determines first_name and last_name. Similarly, the tuple (<First_name>, <Last_name>) determines <Student_id>.

The candidate key for this database is the <Student_Id> because it's the only value that can't be used by another row.