<P> In contrast, if the pizza varieties offered by a restaurant sometimes did legitimately vary from one delivery area to another, the original three - column table would satisfy 4NF . </P> <P> Ronald Fagin demonstrated that it is always possible to achieve 4NF . Rissanen's theorem is also applicable on multivalued dependencies . </P> <P> A 1992 paper by Margaret S. Wu notes that the teaching of database normalization typically stops short of 4NF, perhaps because of a belief that tables violating 4NF (but meeting all lower normal forms) are rarely encountered in business applications . This belief may not be accurate, however . Wu reports that in a study of forty organizational databases, over 20% contained one or more tables that violated 4NF while meeting all lower normal forms . </P> <P> Only in rare situations does a 4NF table not conform to the higher normal form 5NF . These are situations in which a complex real - world constraint governing the valid combinations of attribute values in the 4NF table is not implicit in the structure of that table . </P>

What is fourth normal form in dbms with example