MySQL JOINING 同一张表在 SUM() 上返回错误结果 [重复]

Posted 2023-02-24

【中文标题】MySQL JOINING 同一张表在 SUM() 上返回错误结果 [重复]

【英文标题】：MySQL JOINING same table returns wrong result on SUM() [duplicate]

【发布时间】：2021-12-21 03:58:50

【问题描述】：

我有桌子 Clients 和 Orders

"Clients"             |     "Orders"

ID     NAME           |     ID    SENDER_CLIENT_ID      RECEIVER_CLIENT_ID     PRICE
1      Alex           |     1           1                       3               100
2      Scott          |     2           2                       3               300
3      Philipp        |     3           1                       2               200
                      |     4           1                       2               400
                      |     5           3                       1               300

预期输出：

ID    NAME         SENT_AMOUNT      RECEIVED_AMOUNT
1     Alex            700               300
2     Scott           300               600
3     Philipp         300               400

我的查询输出：

ID    NAME         SENT_AMOUNT      RECEIVED_AMOUNT
1     Alex            700               900
2     Scott           600               600
3     Philipp         600               400

MySQL 查询

SELECT c.id, name, sum(o.price) sent_amount, sum(o2.price) received_amount
FROM clients c LEFT JOIN orders o on c.id = o.sender_client_id LEFT JOIN orders o2 on c.id = t2.receiver_client_id
GROUP BY c.id

当我第二次加入“ORDERS”表时，我认为存在一个问题，因为它可能会带来重复的值，并从那里 SUMs() 重复。如何解决？

【参考方案1】：

尝试独立计算金额

select a.*, s.price send, t.price receive
from clients a 
left join (
  select sender_client_id, sum(price) price
  from orders
  group by sender_client_id
) s on a.id = s.sender_client_id
left join (
  select receiver_client_id, sum(price) price
  from orders
  group by receiver_client_id
) t on a.id = t.receiver_client_id

【讨论】：

不知道我们可以使用 select next 块加入；谢谢。让我检查一下