\begin{frame}
  \frametitle{Foreign Key Constraints}
  
  Once the foreign key is declared,
  the \emph{the following update update operations violate the foreign key constraint}: 

  \begin{alertblock}{}
    \emph{Insertion} into table \sql{Results}\\ without matching tuple in \sql{Students}%
        \begin{itemize}
        \smallskip
          \item DBMS \emph{rejects} the update
        \end{itemize}
        \smallskip
  \end{alertblock}

  \begin{alertblock}{}
    \emph{Deletion} from  table \sql{Students} \\if the deleted tuple is referenced in \sql{Results}
        \begin{itemize}
        \smallskip
          \item DBMS \emph{rejects} the update, or
        \smallskip
          \item deletion \emph{cascades}, that is, tuples in \sql{Results}
            referencing the deleted tuple will also be deleted, or
        \smallskip
          \item the foreign key is \emph{set to null} in \sql{Results}.
        \end{itemize}
     Configure using: \sql{on delete cascade | set null | ...}
  \end{alertblock}
\end{frame}