\begin{frame} \frametitle{Examples} \begin{goal}{} Violations of BCNF might also be due to the \emph{wrong placement of an attribute}. \end{goal} \begin{exampleblock}{Questionable attribute placement} \begin{tcenter} \scalebox{.9}{ \begin{tikzpicture}[every edge/.style={link}] \node[entity] (student) {Students}; \node[entity,xshift=70mm] (course) {Courses}; \node[attribute] [at=(student),shift={(-1cm,1cm)}] {\key{studentId}} edge (student); \node[attribute] [at=(course),shift={(1cm,1cm)}] {\key{courseNr}} edge (course); \node[relationship] at($(student)!.5!(course)$) (takes) {takes} edge node [pos=.7,above] {$0..*$} (student) edge node [pos=.7,above] {$0..*$} (course); \node[attribute] [at=(takes),shift={(0cm,1.4cm)}] {email} edge (takes); \end{tikzpicture} } \end{tcenter} \begin{itemize} \pause \item The relationship is translated into \begin{tcenter} $ \sql{Takes(\underline{studentId}, \underline{courseNr}, email)} $ \end{tcenter} \pause \item Then the FD $\sql{studentId} \to \sql{email}$ violates BCNF. \pause \item Obviously, email should be an attribute of Students. \end{itemize} \end{exampleblock} \end{frame}