\begin{frame}
  \frametitle{Conditional Expressions}

  A typical application is to
  \emph{replace a null value} by a value $Y$:
  \smallskip
    
  \begin{code}{\textwidth}{}
    \small
    \quad\sql{$\cdots$ case when $X$ is not null then $X$ else $Y$ end $\cdots$}
  \end{code}
  \pause\medskip

  In SQL-92, this may be abbreviated to
  \begin{code}{\textwidth}{}
    \small
    \quad\sql{$\cdots$ coalesce ($X$, $Y$)$\cdots$} 
  \end{code}
  \medskip
  
  \begin{code}{\textwidth}{List the addresses of all students}
    \small
    \BUseVerbatim{query}
  \end{code}
\end{frame}

% \overview{6}
\theme{Order By}