\begin{frame}
  \frametitle{Relational Database Schemas}
  
  \begin{block}{Relational database schema}
    A \textbf{relational database schmema} $S$ defines
    \begin{itemize}
      \item a finite set of \textbf{relation names} $\{\,R_1, \dots, R_m\,\}$,
      \item a \textbf{relation schema} $\schema{R_i}$ for every relation $R_i$,
      \item a set of \textbf{integrity constraints} $C$ (defined later).
    \end{itemize}
    In summary, $S = (\, \{\,R_1, \dots, R_m\,\},\, \var{schema},\, C \,)$.  
  \end{block}
  \medskip
  
  \begin{exampleblock}{Example: relational database schema}
    \begin{itemize}
      \item relation names $\{\;\sql{Students},\; \sql{Exercises},\; \sql{Results}\;\}$
      \item relation schema for every relation name
        \begin{itemize}
          \item \headerStudents
          \item \headerExercises
          \item \headerResultsShort
        \end{itemize}
    \end{itemize}
  \end{exampleblock}
  \remark{Examples of integrity constraints: keys and foreign keys.}
\end{frame}