\begin{frame}
  \frametitle{Common Errors}

  \structureStudentsResults
  \smallskip
  
  \begin{code}{\textwidth}{Return those Students which did not
      solve homework 1}
    \small
    \BUseVerbatim{query}
  \end{code}
  \smallskip
  
  \begin{quiz}{\textwidth}{Quiz}
    What goes wrong here?
  \end{quiz}
  \pause
  
  Subqueries bring up the concept of \emph{variable scoping}
  (just like in programming languages) and related pitfalls.
\end{frame}