Normal Forms : Lists and Definitions

1.First Normal Form ( 1NF ) [ Eliminate repeating groups ] :-
When a table has no repeating groups it is said to be in first normal
forms.Means for each cell in a table there can be only one value.This
value should be atomic i.e it cannot be decomposed there.The values
should be simple and indivisible into smaller pieces.

Multivalued attributes , composite attributes , nested relations are split such that they can be made atomic.

-Their should not be any duplicate columns in a table.

2.Second Normal Form ( 2NF ) [ Eliminate redundant data ] :-
If an attribute depends on only part of a multi-valued key, we have to
remove it to a separate table.A table is in second normal form if every
non key column depends on the entire key , just just part of it. The
issue arises only for composite key attribute with multiple columns.

A table is in the second normal form if all of its non key fields are fully dependent on the whole key.

3.Third Normal Form ( 3NF ) [ Remove all columns which are not dependent on the Primary Key ]
:- A relation is in third normal form if it is in 2nd normal form and
non prime attribute is functionally dependent on the other non prime
attribute.

3rd normal form is applied when the relations are in 2NF and there is
any non key attribute that transitively depends on primary key.

I will provide detailed examples on all the normal forms given above.

-Pawan Kumar

Pawankkmr@hotmail.com