\begin{frame} \frametitle{Group By} Grouping by \sql{E.number} \emph{and} \sql{E.topic} yields the desired result! \medskip \begin{code}{\textwidth}{} {\small \BUseVerbatim{query}} \medskip \begin{tcenter} \footnotesize\ttfamily \colorbox{rellight}{% \begin{tabular}{|r|r|r|} \hline \hd{E.number} & \hd{E.topic} & \hd{avg(points)} \\ \hline 1 & Rel.Alg. & 8 \\ 2 & SQL & 8.5 \\ \hline \end{tabular}% } \end{tcenter} \end{code} \vspace{-1ex} Now the DBMS has a \emph{syntactic clue} that \sql{E.topic} is unique. \pause\bigskip \begin{goal}{} The order of the \sql{group by} attributes is not important. \end{goal} \end{frame}