Domain Key In Dbms

It was introduced by ron fagin in his paper a normal form for relational databases that is based on domains and keys acm tods 6 no.

Domain key in dbms. For example a domain of month of year can accept january february december as possible values a domain of integers can accept whole numbers that are negative positive and zero. Historically the process of normalization and the process of discovering undesirable dependencies were carried through 5nf but it has been possible to define the stricter normal form that takes into account additional type of dependencies and constraints. A domain is a unique set of values permitted for an attribute in a table.

Columns in table have a unique name often referred as attributes in dbms. A domain constraint identifies clearly the permitted and enabled values for a given attribute while a key constraint identifies clearly the attributes that distinctly identify a row in a given table or relation. Historically the process of normalization and the process of discovering undesirable dependencies were carried through 5nf but it has been possible to define the stricter normal form that takes into account additional type of dependencies and constraints.

Dk nf domain key normal form unlike previously defined normal forms dk nf is not defined in terms of traditional dependencies functional multivalued or join.