title: sql multiple join and count
body: <p>I have tables like this. but it seems MySQL doesn't count my second join currently. i want to know what i missed for process count of reports for my comment list.</p>
  
  <p><img src="https://i.stack.imgur.com/EGq1p.gif" alt="enter image description here"></p>
  
  <p>and i want to have average of rates also count of reports</p>
  
  <pre><code>SELECT *, avg(rate.score), count(report.id) FROM `comment`
  left join rate on (comment.id = rate.comment_id)
  left join report on (comment.id = report.comment_id)
  group by comment.id
  
  id  text            id      comment_id  score   id      comment_id  type    avg(rate.score)     count(report.comment_id)
  1   good article    1       1           2       1       1           1       4.0000              20
  2   bad article     NULL    NULL        NULL    NULL    NULL        NULL    NULL                0
  </code></pre>
  
  <p><strong>good article</strong> have <strong>2</strong> reports.</p>
  
  <p><code>count(report.id)</code> give me wrong value. what's my mistake?</p>