Normalization

Normalization is process in which database designer redesigns his own database by adding a conditions to the existing database. 

It will be carried out  with a series of tests that can be carried out on individual relation schemas so that the relational database can be normalized to any degree.

When a test fails, the relation violating that test must be decomposed into relations that individually meet the normalization test.

First Normal Form (1 NF)
The domains of attributes must include only atomic values and that the value of any attribute in a tuple must be a single value form the domain of that attribute.

Second Normal Form (2 NF)
A relation to be under Second NF it must have the following constraints
·        It must be in 1st Normal form.
·        All non prime attributes must functionally depend on Prime attribute.

Third Normal Form (3NF)
A relation to be under Third Normal Form it must
satisfy the following constraints.
It must be in 1st and 2nd NF.
No transitive dependency.

Boyce-Code Normal Form (BCNF)
A relation to be under BCNF It must satisfy the
following constraints
·        The relation must be in 3 NF
·        No functional dependency non prime
attribute and candidate keys

Fourth Normal Form

A relation to be under fourth normal form it must
satisfy the following conditions.
It must be in 1st and 2nd NF.
No Multivalued Dependency.

Fifth Normal Form
Fifth normal form addresses the extremely rare case of
join dependencies. A join dependency expresses the cyclical constraint "if Entity1 is linked to Entity2, and Entity2 is linked to Entity3, and Entity3 is linked back to Entity1, then all three entities must necessarily
coexist in the same tuple."

The 12 Rules for RDBMS (Codd’s Rule)

•        Information Representation
•        Guaranteed Access
•        Systematic treatment of Null Values
•        Database Description Rule
•        Comprehensive Data Sub-Language
•        View Updating
•        High-Level Update, Insert, Delete
•        Physical Data Independence
•        Logical Data Independence
•        The Distribution Rule
•        Non Subversion
•        Integrity Rule

Information Representation

All the information is explicitly and logically
represented by data values in the table.
i.e. table, view, column names should be contained
somewhere as a table form.

Guaranteed Access
The table can be taken as storage structure.
The intersection of each column and row there will
necessarily be only one value of data ( or null).
Every value of data must be logically addressable by
using combination of table name, primary key value and column name.

Physical Data Independence
It  is  the ability to modify   the  physical scheme  without  causing application programs to rewritten.

Logical Data Independence

It is the ability to modify the conceptual scheme
without causing application programs to be rewritten.

Integrity Rule

Integrity constraints specific to a particular relational database must be definable in the relational data sub-languages and storable in the catalogue, not in the application programs.

View Updating

It is a myth that all views that can be updated in
theory, can also be updated by the system itself.
It is not possible to update all the views because of
some constraints associated with the tables.

Comprehensive Data Sub-language
The RDBMS must be completely manageable through its
own extension of SQL.

The SQL should support the

·       Data Definition
·       Views
·       Data Manipulation
·       Integrity constraints
·       Authorization
·       Transaction

High - Level Update, Insert Delete

An RDBMS must be more than just be able to retrieve
relational data sets.
It has to be capable of inserting, updating and
deleting data as a relational set.

The Distribution Rule
The RDBMS must have distribution independence.
Database systems built on the relational framework are
well suited to today’s Client / Server Database design.

Non-Subversion
In database management system null values are supported for the representation of missing and inapplicable information.
This support for null values must be consistent
throughout the RDBMS.

Database Description Rule
The description of the database is stored and maintained the form of tables as is done while defining the data.
This allows the users will appropriate authority to
query such information  in the same ways and using the same language as they would any other data in the database.