SQL Group BY、各グループの上位N項目

;WITH s AS 
(
  SELECT StoreID, UPCCode, tds, rn = ROW_NUMBER()
  OVER (PARTITION BY StoreID ORDER BY tds DESC)
  FROM 
  (
    SELECT StoreID, UPCCode, tds = SUM(TotalDollarSales)
    FROM Sales
    GROUP BY StoreID, UPCCode
  ) AS s2
)
SELECT StoreID, UPCCode, TotalDollarSales = tds
FROM s
WHERE rn <= 5
ORDER BY StoreID, TotalDollarSales DESC;