[6.5.3] 'attribute not found'

Using this Query:

explain  SELECT w.counter_id,        ( date_part('month', w.stat_date) || '/' ||          date_part('day', w.stat_date)
 || '/' ||          date_part('year', w.stat_date)  || ' 00:00:00')::datetime as
 
dayperiod,        r.referrer_id, count(w.referrer_hits)   FROM webhit_referer_raw w, referrer_data r, referrer_link l
WHEREw.stat_date < 'Jan 25 2000'    AND w.referrer_url = r.referrer    AND l.counter_id = w.counter_id    AND
l.stat_date= dayperiod    AND l.referrer_id = r.referrer_id
 
GROUP BY dayperiod, counter_id, referrer_id
ORDER BY counter_id, dayperiod;

I get:

ERROR:  attribute 'dayperiod' not found

I'm guessing right now its on: "AND l.stat_date = dayperiod"

Should that not work?  And, I know, its a major mess, just a thought I'm
playing with ... :)

Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
Systems Administrator @ hub.org 
primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org