title: Reference not supported on group function
body: <p>I have some problem using this query, it appears that i cannot use alias as reference on group by query</p>
  
  <pre><code>SELECT v.V_VEHICLEID, v.V_LICENSENO,
  ROUND((MAX(IF(DAY(WP_DATETIME) = 1, WP_ODOMETER, NULL)) - MIN(IF(DAY(WP_DATETIME) = 1, WP_ODOMETER, NULL))) / 1000) AS TRIP1,    
  ...,
  ROUND((MAX(IF(DAY(WP_DATETIME) = 31, WP_ODOMETER, NULL)) - MIN(IF(DAY(WP_DATETIME) = 31, WP_ODOMETER, NULL))) / 1000) AS TRIP31,
  
  ROUND(MAX(IF(DAY(WP_DATETIME) = 1, WP_FUELREAD, NULL)) - MIN(IF(DAY(WP_DATETIME) = 1, WP_FUELREAD, NULL)),2) AS FUEL1,
  ...,
  ROUND(MAX(IF(DAY(WP_DATETIME) = 31, WP_FUELREAD, NULL)) - MIN(IF(DAY(WP_DATETIME) = 31, WP_FUELREAD, NULL)),2) AS FUEL31,
  
  (SELECT TRIP1 / FUEL1) AS ECON1,
  ...,
  (SELECT TRIP31 / FUEL31) AS ECON31
  FROM VEHICLES v
  JOIN WAYPOINTS wp on wp.WP_VEHICLEID = v.V_VEHICLEID
  WHERE MONTH(wp.WP_DATETIME) = '6' AND v.V_USER = 'tc'
  GROUP BY wp.WP_VEHICLEID
  </code></pre>
  
  <p>the error</p>
  
  <blockquote>
    <p>Reference 'TRIP1' not supported (reference to group function)</p>
  </blockquote>
  
  <p>any solution?</p>