Normalization

The process of decomposing tables to eliminate data redundancy is called Normalization.

1^st N.F:- The table should contain scalar or atomic values.

2^nd N.F:- Table should be in 1N.F + No partial functional dependencies

3^rd N.F:-Table should be in 2 N.F + No transitive dependencies

Normalization can be defined as segregating of table into two different tables, so as to avoid duplication of values.

The normalization is a step by step process of removing redundancies and dependencies of attributes in data structure

The condition of data at completion of each step is described as a “normal form”.

Needs for normalization: 

• improves data base design.
• Ensures minimum redundancy of data.
• Reduces need to reorganize data when design is modified or enhanced.
• Removes anomalies for database activities.

First normal form:

• A table is in first normal form when it contains no repeating groups.
• The repeating column or fields in an unnormalized table are removed from the table and put in to tables of their own.
• Such a table becomes dependent on the parent table from which it is derived.
• The key to this table is called concatenated key, with the key of the parent table forming a part it.

Second normal form:

• A table is in second normal form if all its non_key fields fully dependent on the whole key.
• This means that each field in a table must depend on the entire key.
• Those that do not depend upon the combination key, are moved to another table on whose key they depend on.
• Structures which do not contain combination keys are automatically in second normal form.

Third normal form:

 A table is said to be in third normal form, if all the non key fields of the table are independent of all other non key fields of the same table.