\begin{frame} \frametitle{Keys are Functional Dependencies} \begin{block}{Keys are functional dependencies} $\{\, A_1, \dots, A_n \,\}$ is a key of relation $R(A_1,\dots,A_n,B_1,\dots,B_m)$\\ $\iff$ the functional dependency $A_1, \dots, A_n \to B_1, \dots B_m$ holds. \end{block} A \emph{key} uniquely determines \emph{all} attributes of its relation. \pause\medskip \begin{exampleblock}{} \begin{center} \tableCourses \end{center} We have the following functional dependencies: \begin{tcenter} $\sql{courseNr} \to \sql{title}, \sql{instructor}, \sql{phone}$ \end{tcenter} or equivalently: \begin{tcenter} $\sql{courseNr} \to \sql{title}$ \\ $\sql{courseNr} \to \sql{instructor}$ \\ $\sql{courseNr} \to \sql{phone}$ \end{tcenter} \end{exampleblock} \end{frame}