\begin{frame}
  \frametitle{Basic SQL Query Syntax}
  
  \begin{code}{\textwidth}{Basic SQL query (extensions follow)}
    \begin{tcenter}
    $
    \begin{array}{ll}
      \sql{select} & A_1\sql, \dots\sql, A_n \\
      \sql{from}   & R_1\sql, \dots\sql, R_m \\
      \sql{where}  & C
    \end{array}
    $
    \end{tcenter}
  \end{code}
  \ \\[1ex]
  
  The \emph{\sql{from}} clause 
  \begin{itemize}
    \item \ldots declares which \emph{table(s)} are accessed.
  \end{itemize}
  \smallskip
  
  The \emph{\sql{where}} clause 
  \begin{itemize}
    \item \ldots specifies a \emph{condition} for rows in these tables that are considered in this query.
    \item \remark{The absence of $C$ is equivalent to $\sql{true}$.}
  \end{itemize}
  \smallskip
  
  The \emph{\sql{select}} clause
  \begin{itemize}
    \item \ldots specifies the attributes of the \emph{result}.
    \item \remark{Here \sql{*} means output all attributes occurring in $R_1, \dots, R_m$.}
  \end{itemize}
\end{frame}