\begin{frame} \frametitle{Sorting Output} In some application scenarios it is necessary to \emph{add columns} to a table to obtain suitable \emph{sorting criteria}. \begin{exampleblock}{} If the Students names were stored in the form \sql{\textquotesingle{}George\textvisiblespace{}Orwell\textquotesingle{}}, sorting by last name is more or less impossible. Having separate columns for first and last name is better. \end{exampleblock} \pause\bigskip \emph{Null values} are all listed first or all listed last in the sorted sequence (depending on the database). \pause\bigskip \begin{goal}{} Since the effect of \sql{order by} is purely ``cosmetic'',\\ \sql{order by} may \emph{not} be applied to a subquery. \end{goal} \end{frame}