Grade 12 · Theory
Problems with databases
Database Design Concepts · about 4 min
Visual overview: Problems with databases1 MIN READ
2 study sections · pause after each one and recall the key ideaPoorly designed tables develop predictable diseases: redundancy and the three anomalies. Recognising them motivates normalisation.
Key points- Redundancy: the same customer address stored on every order wastes space and invites contradictions.
- Update anomaly: changing a fact requires editing many rows — miss one and data disagrees with itself.
- Insert anomaly: you cannot add a fact because an unrelated fact is missing (can't add a new course until a student enrols).
- Delete anomaly: removing a row destroys unrelated information (deleting the last order loses the customer's details).
- Root cause: unrelated facts crammed into one table.
- Anomaly — an error pattern caused by redundant table design.
- Inconsistency — copies of the same fact disagreeing.
EXAM TIP
given a bad table, point at concrete cells to demonstrate each anomaly — examiners want the demonstration, not the definition alone.