BCNF (Boyce-Codd Normal Form) is a normal form in database normalization that is an extension of the third normal form (3NF) . It is based on functional dependencies that take into account all candidate keys in a relation. A table is in BCNF if every functional dependency X->Y, X is the super key of the table. In simple terms, for any case (lets say, X->Y), X cant be a non-prime attribute.

BCNF is more restrictive than 3NF but less restrictive than the fourth normal form (4NF) . A table that is in 3NF is not necessarily in BCNF. To satisfy BCNF, a table must be in 3NF and for every functional dependency (lets say, X->Y), X must be either the super key or the candidate key.

BCNF is important because it helps to eliminate data redundancy and anomalies in a database. However, BCNF decomposition does not always satisfy dependency preserving property.

In summary, BCNF is a normal form in database normalization that is more restrictive than 3NF but less restrictive than 4NF. It helps to eliminate data redundancy and anomalies in a database by ensuring that every functional dependency X->Y, X is the super key of the table.