我在MySQL中遇到SUM()问题

SELECT Customer, SUM(BalanceAmt) 
FROM billing 
WHERE AttendedBy='attender' AND Customer='CustomerName' 
GROUP BY Customer  

我不知道分配给你的任务是什么。如果您想要客户的金额,则指定为:

SELECT Customer, AssignedTo, SUM(BalanceAmt) 
FROM billing 
WHERE AttendedBy='attender' AND Customer='CustomerName' 
GROUP BY Customer, AssignedTo 

我认为你需要包括一个 where 子句以排除空值。。。下面这样的方法应该可以达到目的:

SELECT Customer, AssignedTo, SUM(BalanceAmt) FROM billing 
WHERE not(BalanceAmt is null) AND AttendedBy='attender' AND Customer='CustomerName'
GROUP BY Customer, AssignedTo

嗯。

SELECT Customer, SUM(BalanceAmt) 
FROM billing 
WHERE AttendedBy='attender' AND Customer='CustomerName' 
GROUP BY Customer

在您的上述查询中 group by 不需要,因为您已将列放在 where 条款。

你可以把它从 select 然后你移除 分组依据 也。

你可以写这样的东西,得到客户明智的总和。

SELECT Customer, SUM(BalanceAmt) 
FROM billing 
WHERE AttendedBy='attender'
GROUP BY Customer;