title: Query fails if no rows are found
body: <p>I have the following query which returns NULL for each field if there are no matching questions or answers for the user. Please can you tell me how I can prevent this from happening?</p>
  
  <p>Thanks!</p>
  
  <pre><code>SELECT u.id, u.first_name, u.last_name, u.email, u.username, COUNT( DISTINCT q.id ) AS  `q_count` , COUNT( DISTINCT a.id ) AS  `a_count` 
  FROM  `users` AS u
  INNER JOIN  `questions` AS q ON u.id = q.uid
  INNER JOIN  `answers` AS a ON u.id = a.uid
  WHERE u.username =  'max'
  LIMIT 0 , 30
  </code></pre>