When developing the schema of a relational database, one of the most important aspects to be taken into account is to ensure that the duplication is minimized. This is done for two purposes:
- Reducing the amount of storage needed to store the data, and
- Avoiding unnecessary data conflicts that may creep in because of multiple copies of the same data getting stored.
Types of Normal Forms
| Normalization works through a series of stages called normal forms. The normal forms apply to individual relations. The relation is said to be in particular normal form if it satisfies constraints. |
|
| Normal Form | Description |
|---|---|
| 1NF | A relation is in 1NF if it contains an atomic value. |
| 2NF | A relation will be in 2NF if it is in 1NF and all non-key attributes are fully functional dependent on the primary key. |
| 3NF | A relation will be in 3NF if it is in 2NF and no transition dependency exists. |
| BCNF | A stronger definition of 3NF is known as Boyce Codd's normal form. |
| 4NF | A relation will be in 4NF if it is in Boyce Codd's normal form and has no multi-valued dependency. |
| 5NF | A relation is in 5NF. If it is in 4NF and does not contain any join dependency, joining should be lossless. |