Glossary

DB Normalization

Normalization is the process of organising tables to minimise data duplication and prevent anomalies on insert, update, and delete. Each normal form imposes stricter requirements.

The first three normal forms

1NF — each cell holds one atomic value (not an array, not a comma-separated list)
2NF — no partial dependencies: every non-key attribute depends on the entire primary key
3NF — no transitive dependencies: non-key attributes depend only on the key, not on other non-key attributes

Denormalization

Normalization reduces redundancy but increases JOINs. In read-heavy systems, data is deliberately denormalized (duplicated) to avoid complex queries. A typical example: storing a username alongside a comment to avoid JOINing to the users table.