Fourth Normal Form (4NF)

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>

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_Listing>

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