\begin{frame} \frametitle{Splitting Relations: Unnecessary Splits} \begin{alertblock}{} Not every lossless split is reasonable! \end{alertblock} \begin{exampleblock}{} \begin{center} {\ttfamily\footnotesize \colorbox{rellight}{% \begin{tabular}{|r|r|r|} \multicolumn{3}{c}{Students} \\ \hline \hd{\underline{sid}} & \hd{first} & \hd{last} \\ \hline 101 & George & Orwell \\ 102 & Elvis & Presley \\ \hline \end{tabular}% }} \end{center} \pause Splitting \sql{Students} into \begin{center} \sql{StudentsFirst(\underline{sid}, first)}\\ \sql{StudentsLast(\underline{sid}, last)} \end{center} is lossless\pause, but \begin{itemize} \item the split is \emph{not} necessary to enforce a normal form, and \item only requires costly joins in subsequent queries. \end{itemize} \end{exampleblock} \end{frame}