SQL3表联合查询的问题

Question

Food 表中有FoodID，FoodName，FoodPrice项
FoodOrder表中有FoodName，Total，OrderID项（FoodName为int型关联到Food表中FoodID项）
OrderTable表中有OrderID,Amount项要实现OrderTable.Amount=sum((FoodOrder.Total*Food.FoodPrice where FoodOrder.FoodName=Food.FoodID) where FoodOrder.OrderID=OrderTable.OrderID)
食物表中有食物ID名称和价格，食物订单中有食物名和数量，订单表中有订单表ID和总额，要计算总额。希望我的问题表述足够清晰……在线等……
具体的SQL语言如何实现？谢谢帮忙……

Answer 1

update
   c
set
   amount=(select sum(b.total*a.foodprice) as num from food a,FoodOrder b where a.foodid=b.FoodName)
from
   food a,FoodOrder b,OrderTable c
where
   a.foodid=b.FoodName and b.OrderID=c.OrderID

Answer 2

update b
set b.Amount=a.sm_Price
from (select b.OrderID,sum(b.Total*a.FoodPrice)  as sm_Price
 from Food a 
  inner join FoodOrder b on a.FoodID=b.FoodName
 group by  b.OrderID
) a
 inner join OrderTable b on b.OrderID=c.OrderID
 

Answer 3

update b
set b.Amount=a.sm_Price
from (select b.OrderID,sum(b.Total*a.FoodPrice)  as sm_Price
 from Food a 
  inner join FoodOrder b on a.FoodID=b.FoodName
 group by  b.OrderID
) a
 inner join OrderTable b on a.OrderID=b.OrderID
 

Answer 4

UPDATE OrderTable SET
       OrderTable.Amount=SUM(FoodOrder.Total*Food.FoodPrice)
FROM   Food  INNER JOIN FoodOrder  ON Food.FoodID=FoodOrder.FoodName
             INNER JOIN OrderTable ON FoodOrder.OrderID=OrderTable.OrderID

Answer 5

UPDATE OrderTable SET
       OrderTable.Amount=SUM(FoodOrder.Total*Food.FoodPrice)
FROM   Food  INNER JOIN FoodOrder  ON Food.FoodID=FoodOrder.FoodName
             INNER JOIN OrderTable ON FoodOrder.OrderID=OrderTable.OrderID
GROUP BY Food.FoodID