mysql 分组错误

Question

下面是我正在使用的查询

SELECT 
  `names`, sum(cashin.amount) as amountin, 
  sum(cashout.amount) as amountout, 
  (sum(cashin.amount) - sum(cashout.amount)) as total 
FROM (`client`) 
INNER JOIN `cashin` ON `cashin`.`clientid`=`client`.`id` 
INNER JOIN `cashout` ON `cashout`.`clientid`=`client`.`id` 
WHERE (sum(cashin.amount) - sum(cashout.amount)) < 0 
GROUP BY `client`.`id`

问题是我得到一个错误:

Invalid use of group function

用字段别名 'total' 替换 where 子句中的函数我仍然得到错误:

Unknown column total

如何修复这个查询？

Answer 1

使用HAVING代替WHERE，并在前面放置GROUP BY names子句而不是GROUP BY id HAVING 子句如下:

SELECT 
  `names`, 
  sum(cashin.amount) as amountin, 
  sum(cashout.amount) as amountout, 
  (sum(cashin.amount) - sum(cashout.amount)) as total 
FROM client
INNER JOIN `cashin` ON `cashin`.`clientid`=`client`.`id` 
INNER JOIN `cashout` ON `cashout`.`clientid`=`client`.`id` 
GROUP BY names
HAVING (sum(cashin.amount) - sum(cashout.amount)) < 0