What is Normalization?

Normalization is the process of removing redundancy in a table so that the table is easier to modify. A number of normal forms have been developed to remove redundancies. A normal form is a rule about allowable dependencies. Each normal form removes certain kinds of redundancies.
Normalization create data that are stored only once on a file. It provides ideal data storage for database systems.
There are three steps of data normalization. The first step is to remove all repeating groups and identify the primary key. The second step is to ensure that all nonkey attributes are fully dependent on the primary key. The third step is to remove any transitive dependencies, attributes which are dependent on other nonkey attributes.

First Normal Form (1NF)
First Normal Form prohibits nesting or repeating groups in tables. A table not in 1NF is unnormalized or non normalized. When a table is in the first normal form, all repeating groups are removed. These groups are moved into a new table. The foreign keys are used to link the tables.

Second Normal Form (2NF)
When a table is in Second normal form, all partial dependencies are removed. A partial dependency is when the data are only dependent on a part of a key field. A relation is created for the data that are only dependent on part of the key and another for data that are dependent on both parts.

Third Normal Form (3NF)
All transitive dependencies are removed. A transitive dependency is when a relation contains data that are not part of the entity. The problem with transitive dependencies is updating the data. A single data item may be present on many records.