4-NF form in DBMS

4-NF form in DBMS

 

In this article, we will learn about the 4-NF form in DBMS.

Normalization is a process of breaking a table into two smaller ones that are free from insertion and deletion and update  problems

4-NF  is the highest level of normalization.

 

Learn more about Normalization in DBMS.

4-NF form in DBMS

Fourth Normal Form

 

Definition of 4th Normal Form

The table is said to be  in 4th Normal Form it is it satisfies the following properties

    • It should be in Boyce Codd normal form(BCNF)
    • It is free from multivalued dependency.

 

What is a multivalued dependency

A Dependency A->B for a single value of  A  there exist multiple values of B, then search dependencies are called as a multivalued dependency

Problem table:

STUDENT

STU_IDCOURSEINTEREST
66_3skProgrammingDrums
66_3skMathAyurveda
73_prashData MiningDrums
79_sanjuWPSSports
82_srinuMathAerobics

 

  • Given table is in First Normal Form because there is no multivalued attribute, it is in second normal form and third Normal Form because it is free from all kinds of partial dependency, full dependency  and transitive dependency and it is in BCNF because in  all the dependencies left side  attribute is a super key
  • Here student id 66 appears two times  in courses and interests column and it leads to unnecessary repetition of data.

 

Procedure to Convert a table to 4-NF

Break the given tables into two different tables ensure that on multiple values are not mapped for a single attribute

STUDENT_COURSE

STU_IDCOURSE
66_3skProgramming
66_3skMath
73_prashData Mining
79_sanjuWPS
82_srinuMath

 

STUDENT_INTEREST

STU_IDINTEREST
66_3skDrums
66_3skAyurveda
73_prashDrums
79_sanjuSports
82_srinuAerobics