\begin{frame}
  \frametitle{Eliminating Tables}

  If participation is \emph{partial} ($0\sldots 1$)
  then replacing the table by an attribute will result in \emph{null values}
  for the entities that do not participate in the relationship set.
    
  \begin{goal}{}
    If participation is \emph{total} ($1\sldots 1$), declare foreign key \sql{not null}.
  \end{goal}
  \pause

  \begin{goal}{}
    For \emph{one-to-one} ($0\sldots 1$ or $1\sldots 1$) relationship sets
    either side can be extended with the key of the other.
  \end{goal}
  \pause
    
  \begin{goal}{}
    Tables for relationship sets linking \emph{weak entity sets} to the identifying entity set can always be eliminated.
    \smallskip

    \emph{No extra table is needed!} The table of the weak entity set already contains the key of the identifying entity set.
  \end{goal}
  \remark{%
    For instance the \textit{payment} table already contains 
    the full information that would appear in the \textit{loan-payment} table (\textit{loan-number} and \textit{payment-number}).
  }
\end{frame}