title: MySQL How to Return Unique/Distinct Results?
body: <p>I'm running the following MySQL query to find cars that don't have manuals (and have black wheels, etc.)</p>
  
  <pre><code>SELECT `cars`.* FROM `cars`
  INNER JOIN wheels ON cars.id = wheels.car_id
  LEFT OUTER JOIN manuals ON cars.id = manuals.car_id
  WHERE (cars.created_at &gt; '2010-09-09'
  AND wheels.color = 'Black'
  AND wheels.created_at &lt; '2011-01-05'
  AND manuals.car_id IS NULL)
  </code></pre>
  
  <p>The results of the query look correct, but it returns the car with id 27 twice. How do I change the query so that all results are unique (no duplicates)?</p>