Fourth Normal Form (4NF)
A multi-valued dependency exists when
- there are at least three attributes A, B, and C in a relation and
- for each value of A there is a well-defined set of values for B, and a well-defined set of values for C,
- but the set of values of B is independent of set C
A relation is in 4NF if it is already in 3NF and has no multi-valued dependencies
Every possible combination of the two multi-valued attributes have to be stored in the database thus leading to redundancy and consequent anomalies