NORMALISATION

Normalisationis a process of organizing the data in database to avoid data redundancyand anomalies .

We have different levels of normal forms 1st,2nd, 3rd , BCNF ,4th,5th etc .

A relation is always specified with its highest normalization level .

First Normal Form defines that all the attributes in a relation must have atomic values .

Second Normal Form is based on the concept of fully functional dependency .

To be in second normal form, a relation must be in First Normal Form and

every non-prim attributes are fully functionally dependent on any of the candidate keys.

A relation is in 3rd normal form ,

1)It must be in 2NF

2)Nonprime attributes should not be transitively dependent on candidate keys.

For a relation to be in Boyce-CoddNormal Form (BCNF  or 3.5 NF),

1.It should be in theThird Normal Form.

2.And, for any dependency X→ Y, X must be asuper key.

Stronger version of 3NF .