title: How can I change this query into a subquery
body: <pre><code>SELECT c.name, c.tel
  FROM Customer c, Vehicle c, Hire h
  Where c.cid=h.cid
  AND v.vid = h.vid
  AND (dropoff-pickup) &gt; 1
  AND v.make = 'Suzuki'
  </code></pre>
  
  <p>dropoff and pickup are just date fields </p>