\begin{frame}
  \frametitle{Cardinalities and Constraints}
  
  When translating entity sets and relationship sets to tables:
  \begin{itemize}
    \item every table should have a \emph{primary key} (if possible)
    \item declared \emph{foreign key constraints} for each relation
  \end{itemize}
  \pause\medskip
  
  \begin{goal}{}
    Foreign keys should be declared
    \begin{itemize}
      \item \emph{not null}, or not, 
      \item \emph{unique}, or not,
    \end{itemize}
    \emph{to model the cardinality limits} as good as possible.
  \end{goal}
  \pause
  
  \begin{exampleblock}{}
    All columns in tables from relationship sets are \textit{not nullable}.\\
    \remark{Each row is a relationship among all participating entity sets.}
  \end{exampleblock}
  \pause\medskip
  
  \begin{goal}{}
    Attributes should be declared \emph{not null} and/or \emph{unique} if appropriate.
  \end{goal}
\end{frame}