title: Group by two fields, and having count() on first field
body: <p>I have a table that stored users play list, a video can be viewed by multiple users for multiple times. 
  A records goes like this:</p>
  
  <pre><code>videoid, userid, time
  123,     abc   , 2013-09-11
  </code></pre>
  
  <p>It means user(abc) has watched video(123) on 2013-09-11</p>
  
  <p>Now I want to find distinct users watched video list (no duplication), and <strong>only show the users that have watched more than two videos</strong>.</p>
  
  <pre><code>SELECT videoid, userid 
  FROM table_play_list
  WHERE SOME CONDICTION
  GROUP BY userid, videoid
  </code></pre>
  
  <p>The sql only select distinct users watchlist, I also want to filter users that have watched more than two different videos. </p>
  
  <p>I know I have to google and read the documentation first, some said 'HAVING' could solve this, unfortunately, I could not make it.</p>