\begin{frame}
  \frametitle{Single Value Subqueries}

  \begin{goal}{}
    If \emph{none of the keywords} \sql{all}, \sql{any}, \sql{some} are present, i.e.
    \begin{tcenter}
      \sql{\ldots where x = (select A from \ldots)}\;,
    \end{tcenter}
    the subquery must yield \emph{single column and \alert{at most one row}}.
    So the comparison is between atomic values.
  \end{goal}
  \pause
  
  \structureAll
  \smallskip
  
  \begin{code}{1\textwidth}{Who got full points for homework 1?}
    \footnotesize
    \BUseVerbatim{query}
  \end{code}
  \pause\vspace{-1.5ex}
  
  \begin{quiz}{\textwidth}{}
    Why is this query guaranteed to return a single column \& row?
  \end{quiz}
  \vspace{10cm}
\end{frame}