title: How can I add a where exists statement in this "group by" mysql query?
body: <p>I have a query that returns the range of a value within groups in the table. </p>
  
  <p>Now I want to check for every group if a value "results" occurs in column "pages", and only if the statements holds true, return the row.</p>
  
  <p>A example of the table structure:</p>
  
  <pre><code>   ID  pages    start_time
      1   splash   12
      1   view     14
      1   comments 16
      1   results  18
      2   splash   1
      2   view     13
      2   comments 14
      2   comments 15
      3   test     2
      3   splash   3
      3   results  35
      3   view     26
  </code></pre>
  
  <p>From this example, the following should be returned:</p>
  
  <pre><code>   ID   time_range
      1    6
      3    33
  </code></pre>
  
  <p>because ID=2 doesn't have row "results" in column pages.</p>
  
  <p>I have the following query, but don't get the additional condition to work.</p>
  
  <pre><code>SELECT MAX(start_time)-MIN(start_time) 
  FROM mytable 
  WHERE country="United States"
  AND (here should come the if-results-in-pages-exists statements) 
  GROUP BY my_id;
  </code></pre>
  
  <p>How can I add this condition properly?</p>