Fourth Normal Form (4NF)

DBMSDatabaseMySQL

What is 4NF?

The 4NF comes after 1NF, 2NF, 3NF, and Boyce-Codd Normal Form. It was introduced by Ronald Fagin in 1977.

To be in 4NF, a relation should be in Bouce-Codd Normal Form and may not contain more than one multi-valued attribute.

Example

Let us see an example −

<Movie>

Movie_Name
Shooting_Location
Listing
MovieOne
UK
Comedy
MovieOne
UK
Thriller
MovieTwo
Australia
Action
MovieTwo
Australia
Crime
MovieThree
India
Drama

The above is not in 4NF, since

  • More than one movie can have the same listing
  • Many shooting locations can have the same movie

Let us convert the above table in 4NF −

<Movie_Shooting>

Movie_Name
Shooting_Location
MovieOne
UK
MovieOne
UK
MovieTwo
Australia
MovieTwo
Australia
MovieThree
India

<Movie_Listing>

Movie_Name
Listing
MovieOne
Comedy
MovieOne
Thriller
MovieTwo
Action
MovieTwo
Crime
MovieThree
Drama

Now the violation is removed and the tables are in 4NF.

raja
Published on 04-Jul-2018 08:18:27
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