Normal forms are rules used to organize data in relational databases (DBs) to eliminate data anomalies and ensure data integrity and accessibility.
The following normal forms exist:
1. First Normal Form (1NF)
All attributes have atomic values (not divisible into smaller ones).
All records (tuples) are unique.
There are no duplicate records.
2. Second Normal Form (2NF)
Meets all 1NF requirements.
Each non-key attribute depends on the entire primary key, not on a part of it.
3. Third Normal Form (3NF)
Meets all 2NF requirements.
There are no transitive dependencies between non-key attributes.
4. Boyce-Codd Normal Form (BCNF)
The relation does not contain transitive dependencies.
Each non-trivial functional dependency is determined by a superkey.
5. Fourth Normal Form (4NF)
Meets all 3NF requirements.
All non-key attributes of multivalued dependencies do not depend on each other.
6. Fifth Normal Form (5NF)
Meets all 4NF requirements.
Decomposition into projections without loss of information.
