\begin{frame}
  \frametitle{Denormalization}
  
  \begin{goal}{}
    \emph{Denormalization} is the process of \emph{adding redundant columns} 
    to the database in order to \emph{improve performance}.
  \end{goal}
  \pause
  
  \begin{exampleblock}{Redundant data storage}
    For example, if an application extensively access the phone
    number of instructors, performance-wise it may make sense to add
    column \sql{phone} to table \sql{Courses}.
    
    \begin{tcenter}
    {\ttfamily\footnotesize
    \colorbox{rellight}{%
      \begin{tabular}[t]{|r|r|r|c|}
        \multicolumn{4}{c}{Courses} \\ \hline
        \hd{\underline{courseNr}} & \hd{title} & \hd{instructor} & \hd{phone} \\
        \hline
      \end{tabular}%
    }}      
    \end{tcenter}
    \pause\medskip
    
    This \emph{avoids the otherwise required joins} (on attribute \sql{instructor}) 
    between tables \sql{Courses} and \sql{Instructors}.
  \end{exampleblock}
\end{frame}