Question

我需要以下方案的帮助。

订单表

orderId    orderAmount
10001      1000.00
10002      2000.00
10003      3000.00
10004      1000.00
10005      1000.00

转移表

transferId    orderId    transferAmount
9001          10001      100.00
9002          10001      200.00
9003          10001      25.00
9004          10002      250.00
9005          10002      450.00
9006          10004      100.00

返回表格

returnId      orderId    returnAmount
8001          10001      450.00
8002          10001      50.00
8003          10002      245.00
8004          10003      100.00

需要的结果

/*include all orders from orders table, even if no transfers or returns*/
orderId       transfers      returns
10001         325.00         500.00 /*sum of transfers and returns per orderId from respective tables*/
10002         700.00         245.00
10003         0.00           100.00
10004         100.00         0.00
10005         0.00           0.00   /*use zero whenever no rows for orderId in respective table*/

如何在单个查询中实现上述内容？

Answer 1

这很棘手。我认为最简单的方法是union all。如果我的算术运算正确，您希望将订单金额添加到转移但不返回：

select orderId,
       sum(transfers) as transfers,
       sum(returns) as returns
from ((select orderId, Amount, 0 as transfers, 0 as returns
       from orders o 
      ) union all
      (select orderId, 0, transferAmount, 0
       from transfers
      ) union all
      (select orderId, 0, 0, returnAmount
       from transfers
      )
     ) otr
group by orderId;

Answer 2

您只需选择所有订单行即可。对于每个订单，您子查询由OrderId链接的表。

SELECT o.orderId
    , (SELECT sum(TransferAmount)
       FROM Transaction t
       WHERE t.OrderId = o.OrderId) 'Transaction'
    , (SELECT sum(r.ReturnAmount)
       FROM Result r
       WHERE r.OrderId = o.OrderId) 'Return'
FROM Order o

Answer 3

我会使用派生表，类似于（如果语法稍微偏离，未经测试，则道歉）：

SELECT  O.OrderID,COALESCE(T.Total,0) AS [Transfer Total],COALESCE(R.Total,0) AS [Return Total]
FROM    Orders AS O
        LEFT JOIN 
        (
        SELECT  T.OrderID,SUM(T.TransferAmount) [Total]
        FROM    Transfer_Table AS T
        GROUP BY T.OrderID
        ) AS T ON O.OrderID = T.OrderID
        LEFT JOIN
        (
        SELECT  R.OrderID,SUM(R.ReturnAmount) [Total]
        FROM    Return_Table AS R
        GROUP BY R.OrderId
        ) AS R ON R.OrderId = O.OrderID

使用SUM连接多个表

3 个答案: