\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}