GROUP BY 与count(*) 连用的时候出现问题，读不到数据

GROUP BY 与count(*) 连用的时候出现问题，读不到数据，后来看网上网友的例子，修改如下：

select COUNT(*) from (
SELECT 
MAX(proSaleBillID) as proSaleBillID,
 proSaleBill.proSaleBillCode,
 proSaleBill.BusiName,
AVG(totalPrice) AS totalPrice ,
MAX(receiptBill.realReciAmount) AS realReciAmount ,
MAX(proSaleBill.totalPrice-receiptBill.realReciAmount)  as remainAmount 
from proSaleBill ,  receiptBill
where proSaleBill.BusiName LIKE  '%2%'  
      and  prosalebill.prosalebillcode=receiptbill.prosalebillcode
      and receiptbill.realreciamount<prosalebill.totalprice
      group by  proSaleBill.proSaleBillCode,BusiName
) as countt

即把要查找数目的数据源放在select count(*)的子句里面。

但是为什么我开始GROUP BY 与count(*) 连用的时候出现问题，读不到数据，这个不大清楚，请哪位大侠知道的给解释一下，不胜感激