SQL 减法问题！

Question

update LotteryPrizesName 
set Prizes_Surplus=Prizes_Total-ss
from
(
SELECT a.jiangpin_no,COUNT(a.jiangpin_no) ss
FROM Lottery a ,LotteryPrizesName b 
WHERE a.jiangpin_no=b.Prizes_No 
GROUP BY jiangpin_no
)b
where b.jiangpin_no = LotteryPrizesName.Prizes_pids

Answer 1

update LotteryPrizesName
set Prizes_Surplus=Prizes_Total- isnull(ss,0)
from LotteryPrizesName t
left join
(
SELECT a.jiangpin_no,COUNT(a.jiangpin_no) ss
FROM Lottery a ,LotteryPrizesName b
WHERE a.jiangpin_no=b.Prizes_No
GROUP BY jiangpin_no
)b
on  b.jiangpin_no = t.Prizes_pids