What is the Boyce-Codd normal form (BCNF) and when is it used?

The Boyce-Codd normal form (BCNF) is a higher level of database normalization that ensures the elimination of certain types of data anomalies. It is used to eliminate functional dependencies where a non-key attribute is functionally dependent on only a part of a candidate key.

BCNF is used when there is a need to further refine the normalization process beyond the third normal form (3NF). It helps in reducing data redundancy and improving data integrity by ensuring that every non-key attribute is functionally dependent on the candidate key. By eliminating partial dependencies, BCNF helps in achieving a higher level of data normalization.

To meet the requirements of BCNF, a relation must satisfy the following conditions:
1. Every determinant (a set of attributes on which other attributes are functionally dependent) must be a candidate key.
2. There should be no partial dependencies, meaning that no non-key attribute should be functionally dependent on only a part of a candidate key.

If a relation does not meet these conditions, it can be decomposed into multiple relations to achieve BCNF. This decomposition involves creating separate relations for each determinant and its dependent attributes.

Overall, BCNF is used to ensure data integrity and eliminate certain types of data anomalies by refining the normalization process beyond 3NF.