\begin{frame}
  \frametitle{Recursive Relations}

  The correct way is to use a \emph{recursive relation}:
  \begin{center}
  \scalebox{.8}{
  \begin{tikzpicture}[every edge/.style={link},d/.style={node distance=1cm}]
    \node[entity] (employee) {employee};
      \node[attribute,at=(employee),d,shift={(200:2.5cm)}] (id) {\key{id}} edge (employee);
      \node[attribute,at=(employee),d,shift={(180:2.5cm)}] (name) {name} edge (employee);
      \node[attribute,at=(employee),d,shift={(160:2.5cm)}] (job) {job title} edge (employee);
      \node[attribute,at=(employee),d,shift={(110:1.5cm)}] (salary) {salary} edge (employee);

    \node[relationship] (supervises) at ($(employee) + (4cm,0cm)$) {supervises} 
      edge[bend left=30] node [above,pos=.75] {$1\sldots *$} (employee) 
      edge[bend right=30] node [below,pos=.75] {$0\sldots 1$} node [above,pos=.5,inner sep=0] {manager} (employee);
  \end{tikzpicture}
  }
  \end{center}
  \pause
  
  \begin{goal}{}
    A \emph{recursive relation} translates to a foreign key that refers to the same table.
  \end{goal}
  
  \centering{\small\ttfamily
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|r|r|r|}
        \multicolumn{5}{c}{Employee}        \\ \hline
        \hd{\key{id}} & \hd{name} & \hd{jobTitle}& \hd{salary} & \hd{supervisedBy$\;\to\;$id} \\ \hline 
        1 & James & \ldots & \ldots & 2  \\
        2 & Harrison & \ldots & \ldots & null \\
        \hline
      \end{tabular}%
    }}
  \pause
  
  \begin{goal}{}
    A \emph{recursive many-to-many relation} requires a separate table
    with two foreign keys to the parent table (the usual translation). 
  \end{goal}
\end{frame}