title: How to get the rows that some of the users did event1 but did not do event2?
body: <p>In this query I am trying to find users who visited the page, but did not see the content. All I can find was this query, but this query is slow so much. Is there any way in your mind that I can find a better solution? Thank you!</p>
  
  <pre><code>SELECT COUNT(*) FROM (
    SELECT u.id FROM users u INNER JOIN ( 
      SELECT pl.user_id FROM visited_logs vl 
      LEFT JOIN seen_logs sl ON sl.user_id = vl.user_id 
      WHERE vl.camp_id IN ('33') AND vl.camp_type = 0 
      AND sl.camp_id IS NULL 
    ) as joined ON joined.user_id = u.id 
    WHERE u.status = 'alive'
  ) derp
  </code></pre>