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

  \structureAll
  \smallskip

  Exercises with corresponding submissions in different ways\ldots
  
  \begin{code}{\textwidth}{Join with \emph{\sql{on}}}
    \small
    \BUseVerbatim{query1}
  \end{code}
  \vspace{-1ex}

  \begin{code}{\textwidth}{Join with \emph{\sql{using}}}
    \small
    \BUseVerbatim{query2}
  \end{code}
  \vspace{-1ex}

  \begin{code}{\textwidth}{Join with \emph{\sql{natural}}}
    \small
    \BUseVerbatim{query3}
  \end{code}
\end{frame}