Normal Forms Based on Primary Keys

Normalization organizes data in a database to reduce redundancy and improve consistency. Primary keys uniquely identify each row, and normal forms define progressive rules based on functional dependencies to eliminate data anomalies.

Types of Keys

Normal Forms

First Normal Form (1NF)

Each column contains atomic values (no arrays or repeating groups), and each row is uniquely identified by a primary key.

Second Normal Form (2NF)

Must be in 1NF. Every non-key column is fully dependent on the entire primary key no partial dependencies. (Relevant when the primary key is composite.)

Third Normal Form (3NF)

Must be in 2NF. No non-key column depends on another non-key column eliminates transitive dependencies.

Boyce-Codd Normal Form (BCNF)

A stricter 3NF. Every non-trivial functional dependency must have a candidate key as its determinant. Applies when a table has multiple overlapping candidate keys.

Fourth Normal Form (4NF)

Must be in BCNF. Eliminates multi-valued dependencies no non-key column depends on a combination of other non-key columns independently.

Summary

Conclusion

Normal forms provide progressive rules for eliminating redundancy based on primary key dependencies. Each level builds on the previous from ensuring atomic values (1NF) to removing multi-valued dependencies (4NF). Proper normalization reduces data anomalies and ensures consistent, maintainable database design.