title: Duplicate column name on JOIN in mysql
body: <p>I've got a problem with this sql</p>
  
  <pre><code>SELECT COUNT( * )
  FROM (
  
    SELECT *
    FROM `user` `t`
    JOIN `user_relation` r ON ( t.user_id = r.follower_id
    OR t.user_id = r.user_id )
    WHERE r.status = "active"
    AND (
      r.user_id =125
      OR r.follower_id =125
    )
    AND t.user_id !=125
    GROUP BY t.username
  )sq
  </code></pre>
  
  <p>I always get an error: "#1060 - Duplicate column name 'user_id' " Can anyone help/explain, what I did wrong?</p>
  
  <p>Thanks in advance
  Jan</p>