Third Normal Form

relational-algebra

Definition

Third Normal Form

A schema $\mathcal{R}$ is in third normal form if for every functional dependency $\alpha \to B$ with attribute $B\in \mathcal{R}$, at least one of the following three conditions holds:

1. $B\in \alpha$, i.e. the functional dependency is trivial
2. $\alpha$ is super key of $R$
3. $B$ is prime

The third normal form is an extension of the second normal form and prevents transitive functional dependencies.