\begin{frame}
  \frametitle{Relational Model}

  In this course, we work with \emph{relational databases}.\\
  View and logical level represent data as \emph{relations/tables}.
  \smallskip
  
  \begin{exampleblock}{Example relational database instance}
    \scalebox{.8}{
    \begin{tabular}{| c | c | c | c |}
    \rowcolor{mblue!20}
    \mc{4}{Customers} 
    \\ \hline \rowcolor{mblue!40}
    \ul{id}  & name & street & city 
    \\ \hline \rowcolor{mblue!20}
    191 & George & 1 Main & London
    \\ \hline \rowcolor{mred!30}
    \anchor{relational-row} 302 & Elvis & 12 East & Amsterdam 
    \\ \hline \rowcolor{mblue!20}
    239 & Lisa & 5 North & New York
    \\ \hline 
    \end{tabular}
    }
    \hfill%
    \scalebox{.8}{
    \begin{tabular}{|c|c|}
    \rowcolor{mblue!20}
    \mc{2}{Accounts} 
    \\ \hline \rowcolor{mblue!40}
    depositor  & \ul{accountnr} 
    \\ \hline \rowcolor{mblue!20}
    191 & 101
    \\ \hline \rowcolor{mblue!20}
    302 & 217
    \\ \hline \rowcolor{mblue!20}
    239 & 205
    \\ \hline 
    \end{tabular}
    }
    \medskip
    \begin{itemize}
      \item \anchor{relational-from}\emph{row = tuple record}:
            (302, Elvis, 12 East, Amsterdam) 
      %\item sequence of columns/attributes
    \end{itemize}
    \begin{tikzpicture}[remember picture,overlay]
      \draw [very thick,->,dblue] ($(relational-from)+(-4mm,0mm)$) -- ++(-6mm,0mm) |- ($(relational-row)+(-2.7mm,1.5mm)$);
    \end{tikzpicture}\vspace{-2ex}%
  \end{exampleblock}
  \medskip

  In the \emph{pure relational model}, a table is a \emph{set} of tuples:%
  \begin{itemize}
    \item has no duplicate tuples (rows)
    \item no order on the tuples
  \end{itemize}  
  
\end{frame}