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SQL-Normalization 

Pooja Goel  |   Nov 16, 2019  |  Views: 26

Description:

Normalization is technique to minimize redundancy means useless data.


Main aim of normalization is to add, delete or modify fields that can be made in single table.


It helps to divide lager table into one or more small tables and link between their relationships.


There are some normal forms:


     1)  First Normal Form (1NF) : This NF should follow the following rules:

  •          Remove all duplicate columns.
  •          It should contain single values.
  •          Multiple Columns cannot be used to fetch the same row.

Example :


Student Table:


StudentName

Age

Subject

Adam

17

Maths, Science

Alex

19

Biology

Lester

21

Maths

 

The following table will consider by using 1NF:

StudentName

Age

Subject

Adam

17

Maths

Adam

17

Science

Alex

19

Biology

Lester

21

Maths

 

    2) Second Normal Form (2NF) : This NF should follow the following rules:

  •         Meets all requirement of INF.
  •         There must not be any partial dependency of any column on Primary Key

 

Example :

Student Table:

Id

StudentName

Subject

1

Adam

Maths

2

Adam

Biology

3

Lester

English

4

Ashlee

Science

 

The following table will consider by using 2NF:

Id

StudentName

1

Adam

2

Lester

3

Ashlee

 

Id

Subject

1

Maths

2

Biology

3

English

4

Science

 

     3) Third Normal Form (3NF) : This NF should follow the following rules:

  •          Meets all requirement of 2NF.
  •          Removing column which are not dependent on Pk Constarint.

 

 

     4)  Fourth Normal Form (4NF) : This NF should follow the following rules:

  •          Meets all requirement of 3NF.
  •          It should not have multi values dependencies.

 

     5) Boyce-Codd Normal Form (BCNF) : This NF should follow the following rules:

  •          Meets all requirement of 3NF.
  •          It should have only one primary key.

 


Comments:
Content Contributor
Pooja Goel

Pooja Goel

Sr. Software developer at Damco Solutions Pvt. Ltd.  |   Noida, Uttar Pradesh, India

I am a sr. software developer working on technologies like SQL, SSIS, SSRS, DB2,Tableau, ASP.NET having 7 years of experience.


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