Domain-Key Normal Form


A relation is in DKNF when insertion or delete anomalies are not present in the database. Domain-Key Normal Form is the highest form of Normalization. The reason is that the insertion and updation anomalies are removed. The constraints are verified by the domain and key constraints.

A table is in Domain-Key normal form only if it is in 4NF, 3NF and other normal forms. It is based on constraints −

Domain Constraint

Values of an attribute had some set of values, for example, EmployeeID should be four digits long −


Key Constraint

An attribute or its combination is a candidate key

General Constraint

Predicate on the set of all relations.

Every constraint should be a logical sequence of the domain constraints and key constraints applied to the relation. The practical utility of DKNF is less.

Updated on 15-Jun-2020 13:36:08