What is Third Normal Form (3NF)?

A table is in Third Normal Form (3NF) when it is in 2NF AND there are no transitive dependencies — non-key attributes should not depend on other non-key attributes. Example: employees(emp_id, emp_name, dept_id, dept_name) — dept_name depends on dept_id (not the PK emp_id), creating a transitive dependency. Fix: split into employees(emp_id, emp_name, dept_id) and departments(dept_id, dept_name). The goal of 3NF is to ensure that every fact is stored in exactly one place — a key principle of good schema design.