title: Composite Primary key vs additional "ID" column?
body: <p>If we had a table like this:</p>
  
  <p>Books (pretend "ISBN" doesn't exist)</p>
  
  <ul>
  <li>Author</li>
  <li>Title</li>
  <li>Edition</li>
  <li>Year of publication</li>
  <li>Price</li>
  </ul>
  
  <p>One could argue that {Author,Title,Edition} could be a candidate/primary key. </p>
  
  <p>What determines whether the candidate/primary key should be {Author,Title,Edition} or whether an ID column should be used, with {Author,Title,Edition} a unique index/key constraint?</p>
  
  <p>So is</p>
  
  <ul>
  <li>Author (PK)</li>
  <li>Title (PK)</li>
  <li>Edition (PK)</li>
  <li>Year of publication</li>
  <li>Price</li>
  </ul>
  
  <p>better, or:</p>
  
  <ul>
  <li>ID (PK)</li>
  <li>Author</li>
  <li>Title</li>
  <li>Edition</li>
  <li>Year of publication</li>
  <li>Price</li>
  </ul>
  
  <p>where {Author,Title,Edition} is an additional unique index/constraint?</p>