sql - 別の列に基づいてある列の合計を取得する方法は?

Question

私の現在のSQLクエリ:

SELECT WorkOrderParts.PartQTY,
       '$' + CONVERT(varchar(22), WorkOrderParts.PartCost, 1) AS PartCost,
       '$' + CONVERT(varchar(22), WorkOrderParts.PartQTY * WorkOrderParts.PartCost, 1) AS PartsTotal,
       tblParts.fldMfgPartNumber
FROM  tblWorkorders
INNER JOIN WorkOrderParts ON tblWorkorders.ID = WorkOrderParts.WorkOrderId
INNER JOIN tblParts ON WorkOrderParts.PartId = tblParts.ID
WHERE (tblWorkorders.ProcessedDate BETWEEN '5/1/2012 12:00:00 AM'
                                       AND '5/2/2012 12:00:00 AM')
GROUP BY tblWorkorders.ProcessedDate, WorkOrderParts.PartCost,
         WorkOrderParts.PartQTY, tblParts.fldMfgPartNumber, tblWorkorders.ID
ORDER BY tblParts.fldMfgPartNumber

返されるデータ:

PartQTY  PartCost  PartsTotal  fldMfgPartNumber 
-------  --------  ----------  ----------------
1        $48.71    $48.71      1878042C91
1        $48.71    $48.71      1878042C91
1        $48.71    $48.71      1878042C91
1        $11.82    $11.82      1R1804
1        $11.82    $11.82      1R1804
1        $11.82    $11.82      1R1804
4        $255.39   $1,021.56   2697041
1        $8.94     $8.94       3719

次の結果を返すように SQL クエリを変更するにはどうすればよいですか。

PartQTY  PartCost  PartsTotal  fldMfgPartNumber 
-------  --------  ----------  ----------------
3        $48.71    $146.13     1878042C91
3        $11.82    $35.46      1R1804
4        $255.39   $1,021.56   2697041
1        $8.94     $8.94       3719