Normalization In Database

  • Post author:
  • Post category:Database
  • Post comments:0 Comments
  • Post last modified:June 3, 2023
  • Reading time:22 mins read

Normalization In Database 

Normalization In Database: The process to convert the complex data structure into simple and stable data structure is called normalization.

The purpose of normalization is to produce a stable set of relations. Basically, a normalized relation has a simple structure, than an un-normalized one. By applying the normalization principles, we can improve the stability of the relations.

Normalization Steps

Normalization is often accomplished in steps, each of which corresponds to a normal form. A normal form is a state of a relation that can be determined by applying simple rules regarding dependencies to that relation.      

A brief description of major steps are given as

First Normal Form (1st NF)

Any repeating group from the relation is removed. After applying this rule, each cell of the relation has a single value.

Second Normal Form (2nd NF)

Any partial functional dependency of the relation is removed.

Third Normal Form (3rd NF)

Any transitive dependency is removed.

Boyce-Cod Normal Form

Every determinant must be a candidate key.

Fourth Normal Form (4th NF)

Any multi-valued dependency is removed.

Fifth Normal Form (5TH NF)

Any remaining anomaly is removed.

The table will be solve by normalization is as follows

First Normal Form

For example the data of employees of an organization is shown as the following table


Employee ID Name Department Salary Course Date Completed
AC-201 Baber Business 25000 MS-Office 06-02-2019
MK-101 Ahmad Marketing 27000 Quality Management 09-09-2017
IT-301 Ali IT 26000 Visual Basic







After the 1st Normal form the table will be show as


Employee ID      Name Department Salary Course Date Completed
AC-201 Baber Business 25000 MS-Office 06-02-2019
MK-101 Ahmad Marketing 27000 Quality Management 09-09-2017
IT-301 Ali IT 26000 Visual Basic 01-02-2013
IT-301 Ali IT 26000 C++ 02-03-2014
IT-301 Ali IT 26000 Java 04-05-2015

Second Normal Form

A relation in the second normal form if and only if it is in the first normal form and all the non key attributes are fully functionally dependent on the key attribute. It is an important step in normalization in database.

In this case

EMPLOYEE (ID, name, Department, salary, Course, Date Completed)

The functional dependencies in this relation are as follows

Emp ID             Name, Dept, Salary

Emp ID, Course             Date Completed



Employee ID      Name Department Salary
AC-201 Baber Business 25000
MK-101 Ahmad Marketing 27000
IT-301 Ali IT 26000
IT-301 Ali IT 26000
IT-301 Ali IT 26000


Course Relation


Employee ID Course Date Completed
AC-201 MS-Office 06-02-2019
MK-101 Quality Management 09-09-2017
IT-301 Visual Basic 01-02-2013
IT-301 C++ 02-03-2014
IT-301 Java 04-05-2015

Third Normal Form

A relation in third normal form if it is in second normal form and no transitive dependency exist.

A third normal form also defined as A non-key attribute must not depend on any other non-key attribute of the relation.

The table of PATIENT-HISTORY (PatientID, Visit Date, Physician, Diagnosis, Treatment)


Patient ID Visit Date Physician Diagnosis Treatment
P-100809 01-02-2104 Dr Ali Chest Infection Free
P-100809 02-03-2015 Dr Ahmad Cold Free
P-100809 03-04-2016 Dr Jawad Hepatitis-A Paid
P-200145 04-05-2017 Dr Ahsan Eye Infection Paid
P-200145 05-06-2018 Dr Usman Cough Free
P-200145 06-07-2018 Dr Atif Flu Free


Now the dependency

DIAGNOSIS (Diagnosis, Treatment)


Diagnosis Treatment
Chest Infection Free
Cold Free
Hepatitis-A Paid
Eye Infection Paid
Cough Free
Flu Free

Fourth Normal Form

A relation is in Fourth Normal Form if and only if it is in Boyce Coded Normal Form and has no multi-valued dependencies.

The table of MEDICINES relation.


Disease Physician Medicine
Cough Dr. Imran

Dr. Tahir

Dr. Asghar



Headache Dr. Imran

Dr. Zahid




After the removing the multi-value dependency the table will be shown as


Disease Physician Medicine
Cough Dr. Imran Actifed-DM
Cough Dr. Tahir Actifed-DM
Cough Dr. Asghar Actifed-DM
Cough Dr. Imran Panadol
Cough Dr. Tahir Panadol
Cough Dr. Asghar Panadol
Headache Dr. Imran Paracetamol
Headache Dr. Zahid Paracetamol
Headache Dr. Imran Panadol
Headache Dr. Zahid Panadol

Fifth Normal Form

A relation is in fifth normal form if it   is in fourth normal form and does not have a join dependency.  It is also known as Project-Join Normal form.

A relation that has a join dependency cannot be divided into two or more relations such that the resulting relations can be re-combined to form the original relation. It is final step of normalization in database.


Data Integrity


We are a team of writers, researchers, and editors who are passionate about helping others live their best lives. We believe that life is a beautiful gift. We try to live our lives to the fullest and enjoy every moment. We are always learning and growing, and we cherish the relationships we have with our family and friends.