\begin{frame}
  \frametitle{Inner and Outer Joins}

  \begin{quiz}{\textwidth}{Will exams appear in the output?}
    \small
    \BUseVerbatim{query}
  \end{quiz}
  \pause
  Yes, exams will appear!
  \smallskip
  
  \begin{alertblock}{}
    Conditions filtering the \emph{left table} make little sense in a
    \emph{left outer join predicate}.
  \end{alertblock}
  The left outer join will make the ``filtered'' tuples appear anyway.
  \pause\medskip
  
  \begin{code}{\textwidth}{Corrected version of last query}
    \small
    \BUseVerbatim{query2}
  \end{code}
\end{frame}