SQL Group By子句（无效列）？

Question

i am building some basic sql query and have come unstuck on a 'group By' clause. I have used alias on my column headers but have hit problems when trying to 'group By' my results. My code at the moment is:-

SELECT                 
  vwREP_GP_ContractProjectPurchaseCostCatID.PACOSTCATID AS COST_CAT_CODE, 
  vwREP_GP_ContractProjectPurchaseCostCatID.PACOSTCATNME AS COST_CAT_NAME, 
  vwREP_GP_ContractProjectPurchaseRpt.COST, 
  vwREP_GP_ContractProjectPurchaseRpt.ITEMDESC AS ITEM, 
  vwREP_GP_ContractProjectPurchaseRpt.CREDITOR, 
  vwREP_GP_ContractProjectPurchaseRpt.DOC_NUM AS DOCUMENT_NUMBER, 
  vwREP_GP_ContractProjectPurchaseRpt.DESCRIPTION, 
  vwREP_GP_ContractProjectPurchaseRpt.DOC_DATE AS DATE,  
  vwREP_GP_ContractProjectPurchaseRpt.PROJECT AS JOB_CODE_STAGE, 
  vwREP_GP_ContractProjectPurchaseRpt.COMPOUNDNAME AS CATEGORY_DESCRIPTION
FROM         
  vwREP_GP_ContractProjectPurchaseCostCatID 
INNER JOIN
  vwREP_GP_ContractProjectPurchaseRpt ON  wREP_GP_ContractProjectPurchaseCostCatID.PACOSTCATID = vwREP_GP_ContractProjectPurchaseRpt.PACOSTCATID


SELECT CATEGORY_DESCRIPTION, SUM(COST) AS TotalCost FROM 
    ( 
        SELECT COMPOUNDNAME AS CATEGORY_DESCRIPTION FROM wREP_GP_ContractProjectPurchaseRpt
    ) A 
GROUP BY CATEGORY_DESCRIPTION

Having added in extra code to deal with using alias column names I now get an error that 'COST' is an invalid column? I have not changed this column name??

I know its something obvious staring at me but my brain is not engaging so if anyone can point out where I am going wrong or a simplier way of doing this that would be a great help.

Thanks in advance.

(this is all being done on sql server management studio 2005)

Answer 1

Use

SELECT COMPOUNDNAME AS CATEGORY_DESCRIPTION, 
       Sum(COST) AS TotalCost 
FROM   vwREP_GP_ContractProjectPurchaseRpt 
GROUP  BY COMPOUNDNAME 

instead of

SELECT  CATEGORY_DESCRIPTION,SUM(COST)AS TotalCost FROM 
( 
    SELECT COMPOUNDNAME AS CATEGORY_DESCRIPTION FROM vwREP_GP_ContractProjectPurchaseRpt
) A 
GROUP BY CATEGORY_DESCRIPTION

You were not including the COST column in inner query.

Answer 2

SELECT  CATEGORY_DESCRIPTION, SUM(COST) AS TotalCost
FROM    ( 
        SELECT COMPOUNDNAME AS CATEGORY_DESCRIPTION, COST
        FROM   vwREP_GP_ContractProjectPurchaseRpt
        ) A 
GROUP BY
        CATEGORY_DESCRIPTION