title: Finding and selecting best publisher by number of books
body: <p>I have homework assignment, which requires to output one or more publishers, which's the most unique books are borrowed at the library. Sorry if it's hard to understand.</p>
  
  <p>I tried following query:</p>
  
  <pre><code>SELECT Book.Publisher, COUNT(DISTINCT Book.Title)
  FROM Book, LibraryInventory
  WHERE LibraryInventory.BorrowedBy IS NOT NULL
  GROUP BY Book.Publisher
  </code></pre>
  
  <p>It shows all publishers and how many unique books are borrowed, however assignment requires only best publisher(s).</p>
  
  <p>Any suggestions how this can be accomplished?</p>