title: "Where" statement based on result of a join
body: <p>When I run this:</p>
  <pre><code>select songs.name,
  count(performances.songid) as performances
  from table_songs songs
  left join table_songperformances performances on songs.id = performances.songid
  group by songs.id desc  
  ORDER BY `songs`.`id`  DESC
  </code></pre>
  <p>I get some results where the number of performances is equal to zero. I want to change my query to only return those results, but &quot;where performances == 0&quot; doesn't work.</p>
  <p>I know this is simple, but I haven't been able to figure it out. Thanks for any help!</p>