\begin{frame}[fragile] \frametitle{Relational Model: Schema} \begin{block}{Database schema} = structure of the database, that is, relations + constraints \end{block} \begin{exampleblock}{Example schema} \begin{itemize} \item Customers(\ul{id}, name, street, city) \item Accounts(depositor $\to$ Customers(id), \ul{accountnr}) \end{itemize} \end{exampleblock} \medskip \begin{block}{Database instance} = actual content (`state') of the database at some moment \end{block} \vspace{-.5ex} \begin{exampleblock}{Example instance} \scalebox{.8}{ \begin{tabular}{| c | c | c | c |} \rowcolor{mblue!20} \mc{4}{Customers} \\ \hline \rowcolor{mblue!40} \ul{id} & name & street & city \\ \hline \rowcolor{mblue!20} 191 & George & 1 Main & London \\ \hline \rowcolor{mblue!20} 239 & Lisa & 5 North & New York \\ \hline \end{tabular} } \hfill% \scalebox{.8}{ \begin{tabular}{|c|c|} \rowcolor{mblue!20} \mc{2}{Accounts} \\ \hline \rowcolor{mblue!40} depositor & \ul{accountnr} \\ \hline \rowcolor{mblue!20} 191 & 101 \\ \hline \rowcolor{mblue!20} 239 & 205 \\ \hline \end{tabular} } \end{exampleblock} \end{frame}