Ошибочное или пропущенное зарезервированное слово или аргумент в инструкции SELECT

SELECT w.NAZV_SKLADA, MAX(s.STOIM) AS MAX_STOIM, MIN(s.STOIM) AS MIN_STOIM, SUM(s.STOIM*s.KOL)/SUM(s.KOL) AS avg STOIM
FROM KNIGI AS b,SKLAD AS w, PROD AS s
WHERE b.ID_KNIGI=s.ID_KNIGI AND s.ID_SKLAD=w.ID_SKLAD AND b.ID_KNIGI= :id
GROUP BY b.ID_KNIGI, w.NAZV_SKLADA
ORDER BY avg STOIM DESC

SELECT ... SUM(s.STOIM*s.KOL)/SUM(s.KOL) AS avg STOIM

ORDER BY avg STOIM DESC

SELECT w.NAZV_SKLADA, MAX(s.STOIM) AS MAX_STOIM, MIN(s.STOIM) AS MIN_STOIM, (SUM(s.STOIM*s.KOL)/SUM(s.KOL)) AS avg_STOIM
FROM KNIGI b,SKLAD w, PROD s
WHERE b.ID_KNIGI=s.ID_KNIGI AND s.ID_SKLAD=w.ID_SKLAD AND b.ID_KNIGI= :id
GROUP BY b.ID_KNIGI, w.NAZV_SKLADA
ORDER BY avg_STOIM DESC

SUM(s.STOIM*s.KOL)/SUM(s.KOL)

SELECT w.NAZV_SKLADA, MAX(s.STOIM) AS MAX_STOIM, MIN(s.STOIM) AS MIN_STOIM, 
          (SUM(s.STOIM*s.KOL)/SUM(s.KOL)) AS avg_STOIM
   FROM KNIGI b,SKLAD w, PROD s
   WHERE b.ID_KNIGI=s.ID_KNIGI AND s.ID_SKLAD=w.ID_SKLAD AND b.ID_KNIGI= :id
   GROUP BY b.ID_KNIGI, w.NAZV_SKLADA
   ORDER BY SUM(s.STOIM*s.KOL)/SUM(s.KOL) DESC

SELECT A.* FROM 
   (
 SELECT w.NAZV_SKLADA, MAX(s.STOIM) AS MAX_STOIM, MIN(s.STOIM) AS MIN_STOIM, 
          (SUM(s.STOIM*s.KOL)/SUM(s.KOL)) AS avg_STOIM
   FROM KNIGI b,SKLAD w, PROD s
   WHERE b.ID_KNIGI=s.ID_KNIGI AND s.ID_SKLAD=w.ID_SKLAD AND b.ID_KNIGI= :id
   GROUP BY b.ID_KNIGI, w.NAZV_SKLADA
   ) A
ORDER BY A.avg_STOIM DESC