\frametitle{Example: Books and Authors}
    \item $\sql{ISBN} \to \pause \sql{TITLE}, \sql{PUBLISHER}$ (ISBN uniquely identifies a book)
    \item $\sql{ISBN} \to \sql{AUTHOR}$ \;\;? \pause \alert{Does not hold.}
    \item $\sql{AUTHOR} \to \sql{TITLE}$ \;\;? \pause \alert{Does not hold in general.}
    \item $\sql{TITLE} \to \pause \sql{nothing}$ (There may be books with the same title)
    \item $\sql{ISBN}, \sql{NO} \to \pause\sql{AUTHOR}$
    \item $\sql{ISBN}, \sql{AUTHOR} \to \sql{NO}$ \;\;? \pause \alert{questionable} (e.g. Smith \& Smith)
    \item $\sql{PUBLISHER}, \sql{TITLE}, \sql{NO} \to \sql{AUTHOR}$ \;\;? \pause \alert{questionable}\\[-0.5ex]
      \remark{Authorship sequence might change in a new edition of a book!}
      During database design, \emph{only unquestionable conditions should be used
      as functional dependencies}.
        Database normalization \emph{alters the table structure} depending 
        on the specified functional dependencies.\\
        \remark{Later hard to change: needs creation/deletion of tables!}