Normalization is the process of creating and organizing data in the database. Database designed abiding the rules of normalization would have the most consistency and do not have redundant information stored. If a database allows redundant information, then there is a potential chance of loss of more disk space due to the duplicate data. Normalization methods help to eliminate redundancy and inconsistent data dependency between the data stored in the database.

What is Redundancy?
The same information stored in multiple tables, Example if a customer address is maintained in two different tables then it is called a redundancy. We need to eliminate redundancy so as to prevent the complexity that arises whenever there is a need to change or update such records. If the customer address needs an update, If the database design did not eliminate redundancy, then address has to be changed in all the places in the database. If the database design had eliminated redundancy with the help of normalization, the customer address of the customer in the customer master table alone needs an update.

What is inconsistent dependency?
It is accurate to search for the address of a customer in the customer table, but it is inappropriate to look for information on the salary of the sales employee who calls the customers in the customer table. These are called inconsistent dependencies. The salary of employees would be maintained in the Employee table which would be logically connected to the customer table on some key fields. If there is any inconsistent dependency it would end up in a complex search to retrieve the data as there might be no logical path defined for the search accurately.

To eliminate redundancy and inconsistent dependency among the database objects, there exist normalization rules for designing a database. These rules are called the Normal Forms. Normal forms exist up to 6th normal form however the first four normal forms are widely used and popular database normalization techniques.

First Normal Form:

• Eliminates repeating groups or duplicate columns in the same table.
• Creates a different table for each set of related attributes.
• Identify each set of related records in the table with the help of a primary key field.

Second Normal Form:

• Has all the rules like First Normal Form.
• Creates a different table may be a master table for set of values that apply to multiple records.
• Creates a link between the different tables with the help of primary and foreign key relationships.

Third Normal Form:

• Has all the rules like Second Normal Form
• Eliminates data field in the table which doesn’t depend on the key field of the table.

Fourth Normal Form:

• Has all the rules like Third Normal Form
• Eliminates the multi valued dependency of the table relations.

The Normalization techniques or rules are a guideline to the database design.

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