Third normal form

Learn third normal form (3NF).

3NF

3NF is in 2NF with no transitive dependency. Non-key columns cannot depend on each other.

-- customers(id, city, postal_code, city_name)
-- city_name → city → id : geçişli bağımlılık

Move city_name to a cities table.

3NF removes transitive dependencies. In A → B → C, you move C to a separate table.

For example, if orders holds customer_id and customer_city, the city really depends on the customer, so it moves to the customers table.

Move city_name to a cities table to reach 3NF.

Show example solution

CREATE TABLE cities (
  id INT PRIMARY KEY,
  name VARCHAR(50)
)

3NF dependency

3NF: no transitive ____ allowed

Show answer

3NF: no transitive dependency allowed

Next lesson: BCNF