mysql - 添加一些列并减去另一列

Question

我有两个表 insert1 和 received1 在 insert1 表中有列，列名是 recharge_account。 received 表只有一列，列名是received_amount。

我想将 recharge_ammount - total received_amount 作为会费。

recharge_Account       Received_Amount     dues
500              -        400               100

SELECT
    SUM(Account_recharge) AS `Total Recharge`,
    SUM(Amount_Received) AS `Total Received`,
    SUM(Account_recharge) - SUM(Amount_Received) AS dues
FROM insert1 i1
INNER JOIN received1 r1

我无法准确计算。

Answer 1

您只需要一个连接条件，例如 ON i1.id = r1.ins_id，以及针对空值的 COALESCE() 函数:

SELECT
    SUM(COALESCE(Account_recharge,0)) AS `Total Recharge`,
    SUM(COALESCE(Amount_Received,0)) AS `Total Received`,
    SUM(COALESCE(Account_recharge,0)) - SUM(COALESCE(Amount_Received,0)) AS dues
FROM insert1 i1
JOIN received1 r1 ON i1.id = r1.ins_id