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Normalization is a process of organizing the data in such a way that data is easily accessed, managed and modified.

Normal forms:

The commonly used four normal forms are first(1NF), second(2NF), third(3NF) and Boyce Codd normal form(BCNF). The other normal forms are fourth(4NF) and fifth(5NF).

First normal form:-

The row of data in a table should not contain repeated group of data i.e. each column should have unique value. Each record in a table should have a unique identifier, primary key.

Non-Normalized table :


This can be normalized in 1NF by creating 2 separate tables

Student Table: Subject table :


Second normal form(2NF)

A table is said to be in 2NF, if it

  • Satisfies 1NF
  • No partial dependency of any column on primary key.

Customer Table:



To reduce this into second normal form, create 3 different tables.



Product table:


Sales Table:


Third Normal form (3NF)

A table or relation is said to be in 3NF if,

  • It satisfies 2NF
  • Every non-prime attribute in the table should depend on primary key. The functional transitive dependency is removed from the table. This helps in reducing the data duplication and achieves data integrity.

Employee table:


This will be in 3NF when ZIPcode table is created as addr1, city, state is dependent on zipcode



Address table:


Boyce & Codd normal form (BCNF)

BCNF is a higher version of 3NF. A 3NF table doesn’t have multiple candidate keys.

Fourth normal form

A table is said to be in 4NF if,

  • It satisfies 3 NF
  • A record should not contain two or more independent multi values about an entity. 

Said t

Fifth Normal Form

A table is said to be in 5NF if,

  • It satisfies 4NF
  • The table consists of a key and non-key attribute only.

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