3NF

Conditions

• Relations has to be in 2NF
• No transitive dependencies on the primary key

A relation is in 3NF if at least one of the following condition holds in every non-trivial function dependency X –> Y

1. X is a super key.
2. Y is a prime attribute (each element of Y is part of some candidate key).

Violation Example

Student ID	Student Name	Course Name	Course Professor	Professor Office Number
1001	Alice Smith	Math 101	Dr. Brown	204
1002	Bob Johnson	History 201	Dr. Johnson	301
1003	Jane Doe	English 101	Dr. Green	203
1004	John Smith	Math 101	Dr. Brown	204

Professor Office Number is fully dependent on Course Professor, which is a non-prime attribute, thus Professor Office Number is transitively depending on the primary key Student ID through Course Professor as it is dependent on the primary key. This this a violation of 3NF.