Normalization

Normalization is a process of reconstructing the original table into several subset tables having few columns and more rows. The main idea behind normalization is to use the storage space efficiently, eliminate the redundant data and reduce or simply eliminate the inconsistent data.
The normalization process has various forms which are known as ”normal forms”. Generally there are many normal forms, but only three normal forms are used. Normal forms increase the efficiency of the database.

First Normal Form (1NF)
First normal form eliminates repeating groups, which means, for each set of related attributes, a separate table must be made and each table has its own primary key.

Second Normal Form (2NF)
An entity is in 2NF if, and only if, it is in 1NF and redundant data is eliminated. Therefore if an attribute depends on only a part of multi-valued key, a separate table must be build containing that attribute.

Third Normal Form (3NF)
An entity is in 3NF if, and only if, it is in 2NF and the columns that doesn’t depend on the table’s primary key are eliminated, thus in this normal form all the columns in the table contains the data about the entity which is defined by the primary key.

Boyce-Codd Normal Form (BCNF)
A 3NF relation would be in BCNF if
(a) multiple candidate keys are eliminated from the table,
(b) the keys are not composed of multiple attributes
(c) common attributes between the keys are not there.

Fourth Normal Form (4NF)
An entity is in Fourth Normal Form (4NF) if, and only if, it is in 3NF and has no multiple sets of multi-valued dependencies. Fourth normal form affects the relationship, as it eliminates multiple independent relationships. Thus many-to-many or many-to-one relationships which are not directly related would not be more than one in a table.

Fifth Normal Form (5NF)
An entity is in Fifth Normal Form (5NF) if, and only if, it is in 4NF and every join dependency for the entity is a consequence of its candidate keys.