MySQL Normalization: 1NF, 2NF and 3NF with Examples

Normalization organises tables to eliminate duplicate data and the anomalies it causes. The first three normal forms cover almost all practical design work — and they're a staple of every database interview.

Key Points

• 1NF: atomic values, no repeating groups — one value per cell
• 2NF: 1NF + no partial dependency on part of a composite key
• 3NF: 2NF + no transitive dependencies (non-key → non-key)
• Fixes anomalies: update in one place, no orphan inserts or deletes
• Practical smell test: the same fact typed in many rows means normalise
• Example: split orders(customer_name, customer_city, …) into customers + orders