title: Operand Should Contain 1 Column - MySQL NOT IN
body: <pre><code>SELECT * from campaigns WHERE id not in
  (SELECT 
      e.id_campaign, d.name, d.frequency, d.country, d.referral, d.bid, d.status, COUNT(e.id) AS countcap  
      FROM campaigns d
      LEFT JOIN served e
      ON d.id = e.id_campaign 
      WHERE 
          d.status = 'Active'
      GROUP BY e.id_campaign
      HAVING
          countcap &lt; d.frequency)
  </code></pre>
  
  <p>I get the error "Operand Should Contain 1 Column" - but I need the COUNT(e.id)</p>