title: MySQL query "more than one row"
body: <p>Hi I have a mysql query below</p>
  
  <pre><code>SELECT `company`,`type`,`code` FROM `location` WHERE (
  SELECT code FROM meter WHERE `meter`.`location_code`=location.code AND meter.code NOT IN (
  SELECT meter_code FROM reading
  ))
  </code></pre>
  
  <p>I receive an error saying that more than one row is returned</p>
  
  <p>Can I ask why/have guidance</p>
  
  <p>Other questions haven't really helped me to be honest</p>