Grade 12 · Theory
How to get rid of anomalies
Database Design Concepts · about 4 min
Visual overview: How to get rid of anomalies1 MIN READ
2 study sections · pause after each one and recall the key ideaNormalisation splits a bloated table into related tables so each fact lives once — eliminating the anomalies at their source.
Key points- 1NF: atomic values only; no repeating groups or lists in a cell; every row unique via a key.
- 2NF: every non-key field depends on the WHOLE primary key (fixes composite-key tables).
- 3NF: no non-key field depends on another non-key field (move it to its own table).
- Result: more tables linked by foreign keys; queries JOIN them back together.
- Practical target: 3NF for operational databases; warehouses may deliberately denormalise.
- Normalisation — the step-by-step decomposition into well-formed tables.
- Functional dependency — field B is determined by field A.
EXAM TIP
practise normalising a small order table to 3NF, showing the tables and keys at each stage — a near-guaranteed exam task.