Normalisering er processen med at organisere data for at reducere redundans og forbedre integritet ved at opdele data i relaterede tabeller, efter en serie af "normale former". Målet: hver datadel lagres én gang, hvilket undgår duplikering og de anomalier, det forårsager.
Problemet: en denormaliseret (redundant) tabel
❌ orders table with everything in one place — data is DUPLICATED:
order_id | customer_name | customer_email | product | price
1 | Ann | [email protected] | Phone | 999
2 | Ann | [email protected] | Case | 20 ← Ann's info repeated!
Problems (anomalies):
✗ UPDATE anomaly — change Ann's email → must update EVERY one of her orders
✗ INSERT anomaly — can't add a customer without an order
✗ DELETE anomaly — deleting Ann's last order loses her info entirely
✗ Wasted storage and inconsistency risk
