Normalization

Normalization

Normalization means branch of relational theory providing design insights.

Goals

1)be able to characterise the level of redundancy in a relational schema

2)provide mechanisms for transforming schemas  to remove redundancy

Normal Forms 

Normalization theory defines six normal forms(NFS)

1)First, Second, Third Normal Forms (1NF,2NF,3NF)

2)Boyce-Codd Normal Form(BCNF)

3)Fourth Normal Form(4NF)

4)Fifth Normal Form(5NF)

NF hierarchy: 5NF⇒4NF⇒BCNF⇒3NF⇒2NF⇒1NF

1NF allows most redundancy; 5NF allows least redundancy

1NF

All attributes have atomic values. This is the basic requirement of every relation schema, in other words every relation schema is in 1NF

2NF

All non-key attributes fully depend on key. This can avoid much redudancy

3NF

No attributes depend on non-key attributes