Domain Key Normal Form DKNF

By Prof. Fazal Rehman Shamil
Last modified on June 28th, 2020

Domain Key Normal Form DKNF is also called 6NF.

Our relations have no constraints other than domain constraints and key constraints.

Domain constraints

Domain constraints specify the possible values of the attribute.

E.g. The only colors of hair are black and white

E.g. The CGPA of a student is between 0 and 4.

Key constraints

Key constraints specify keys of some relation.

General constraints

General constraints or any other constraints which can be

expressed by the first-order logic.

E.g. If the first digit of a bank account is 2, then the balance of

the account is greater than >=4000.

account Balance Type
1-T4Tutorials-110
2-T4Tutorials-211

It’s logically wrong because Balance is nonprime attribute and determining the type. In this case, a transitive dependency is occurring.

Domain Key Normal Form DKNF

Domain constraint: If Regular_Account, then the first digit of  AccountNo will be  2 and balance < 4000

 Domain constraint: If Executive_Account, then the first digit of AccountNo will be 1 and balance ³ 4000.

Solution: Separate table for  Regular_Account and Executive_Account.

account Balance
1-T4Tutorials-110
2-T4Tutorials-211

Table: Regular_Account

 

account Balance
1-T4Tutorials-110
2-T4Tutorials-211

Table: Executive _Account

Keywords: domain key normal form.
domain key normal form in DBMS.
domain key normal form example.
what is the domain key normal form?
domain key normal form in DBMS with example.
domain key normal form ppt.
domain key normal form in DBMS ppt.
define the domain key normal form.
domain key normal form in the DBMS tutorial.
what is domain-key normal form?
domain key normal form in DBMS pdf.

Prof.Fazal Rehman Shamil (Available for Professional Discussions)
1. Message on Facebook page for discussions,
2. Video lectures on Youtube
3. Email is only for Advertisement/business enquiries.