Most 3NF relations are also BCNF relations.

A 3NF relation is NOT in BCNF if:

Candidate keys in the relation are composite keys (they are not single attributes)

There is more than one candidate key in the relation, and

The keys are not disjoint, that is, some attributes in the keys are common.



Any relation is in Fourth Normal Form if it is BCNF and any multivalued dependencies are trivial.

Eliminate non-trivial multivalued dependencies by projecting into simpler tables



A relation is in 5NF if every join dependency in the relation is implied by the keys of the relation.