domain key paradigm

#A relationship is in DKNF when there are no insertion or deletion exceptions in the database. Domain key normalization is the highest form of normalization. The reason is that insert and update exceptions have been removed. Constraints are validated through domain and key constraints.

Only when the table is in 4NF, 3NF, etc., the table is in domain-key normal form. It is based on constraints-

Domain constraints

The value of the attribute has a set of values, for example, EmployeeID should be four digits-

##0921Tom330922Jack#31

EmpID	EmpName	EmpAge

Key constraints

Attributes or combinations thereof are candidate keys

General constraints

Predicate on the set of all relations.

Each constraint should be a logical sequence of domain constraints and key constraints that apply to the relationship. DKNF has less practical utility.

The above is the detailed content of domain key paradigm. For more information, please follow other related articles on the PHP Chinese website!