MySQL：使用两个表的总和更新值

我有一张这样的桌子

负债：

Id | CustomerId | liabilities
---------------------------
9    90           1000
...

Id | CustomerId | Payment
---------------------------
3    90           2500
4    91           1000
...

Id | balance
---------------------------
90   1500
91   1000
...

付款：

Id | CustomerId | liabilities
---------------------------
9    90           1000
...

Id | CustomerId | Payment
---------------------------
3    90           2500
4    91           1000
...

Id | balance
---------------------------
90   1500
91   1000
...

客户：

Id | CustomerId | liabilities
---------------------------
9    90           1000
...

Id | CustomerId | Payment
---------------------------
3    90           2500
4    91           1000
...

Id | balance
---------------------------
90   1500
91   1000
...

---

如您所见，客户的余额是其所有付款的总和减去其所有负债的总和。什么是更新余额的SQL查询？

您可以使用

update

语句对包含

付款

和

负债

合计的派生表执行

左联接

操作：

UPDATE Customer AS c
LEFT JOIN (
  SELECT CustomerId, SUM(Payment) AS TotalPayment
  FROM Payments
  GROUP BY CustomerId
) AS p ON c.Id = p.CustomerId
LEFT JOIN (
  SELECT CustomerId, SUM(liabilities) AS TotalLiabilities
  FROM Liabilities
  GROUP BY CustomerId
) AS l ON c.Id = l.CustomerId  
SET balance = COALESCE(TotalPayment, 0) - COALESCE(TotalLiabilities, 0)

或者，您可以在

UPDATE

语句中使用相关子查询：

UPDATE Customer AS c 
SET balance = COALESCE((SELECT SUM(Payment) 
                        FROM Payments 
                        WHERE CustomerId = c.Id) , 0)
              - 
              COALESCE((SELECT SUM(liabilities) 
                        FROM Liabilities 
                        WHERE CustomerId = c.Id)  , 0)

---

您可以使用

UPDATE

语句对包含

付款

和

负债

合计的派生表执行

左联接

操作：

UPDATE Customer AS c
LEFT JOIN (
  SELECT CustomerId, SUM(Payment) AS TotalPayment
  FROM Payments
  GROUP BY CustomerId
) AS p ON c.Id = p.CustomerId
LEFT JOIN (
  SELECT CustomerId, SUM(liabilities) AS TotalLiabilities
  FROM Liabilities
  GROUP BY CustomerId
) AS l ON c.Id = l.CustomerId  
SET balance = COALESCE(TotalPayment, 0) - COALESCE(TotalLiabilities, 0)

或者，您可以在

UPDATE

语句中使用相关子查询：

UPDATE Customer AS c 
SET balance = COALESCE((SELECT SUM(Payment) 
                        FROM Payments 
                        WHERE CustomerId = c.Id) , 0)
              - 
              COALESCE((SELECT SUM(liabilities) 
                        FROM Liabilities 
                        WHERE CustomerId = c.Id)  , 0)

---

你可以考虑安排的事件，这里有更多的信息：这是一个很好的观点。但在这一点上，我其实只是想得到一个查询，将做更新。。。然后，事件是个好主意。你可以考虑安排的事件，这里有更多的信息：这是一个很好的观点。但在这一点上，我其实只是想得到一个查询，将做更新。。。那么这些活动就是一个好主意。