title: ER-Diagram and SQL DDL for a library database
body: <p>I'm trying to draw an ER-diagram and SQL ddl for a simple library database.</p>
  
  <p>I have the following entities:</p>
  
  <pre><code>Book (holds the ISBN as key, book title, author)
  Copy (copyID of a copy of a book, dateAcquired, dateDestroyed)
  Member (MemberID, name, address)
  Loaned (i guess the date due and the date back and obviously foreign keys for memberID and copyID)
  </code></pre>
  
  <p>Also a Member can be <strong>Student</strong> or <strong>Staff</strong>. So i think this should be a "IS-A" relationship.</p>
  
  <p>How can i represent this in a proper ER-Diagram and SQL-DDL</p>