Question

让我感到困惑..总左计算似乎不起作用。

我正在尝试获得总凭证并获得总使用量和总剩余数。

请帮忙。

SELECT 
 (IFNULL(SUM(value), 0)) AS total_voucher,
 (
  SELECT 
    IFNULL(SUM(value), 0))
  FROM 
    voucher_history 
  WHERE 
    idUser = 1 AND isUsed = 1 AND DATE(FROM_UNIXTIME(datetime)) = '2014-03-04'
 )  AS total_used,

 (total_voucher-total_used) AS total_left

FROM 
 voucher_history 
WHERE 
 idUser = 1 AND isUsed = 0 AND DATE(FROM_UNIXTIME(datetime)) <= '2014-03-05'

Answer 1

您可以使用条件聚合执行此操作，而不是使用子查询：

SELECT coalesce(SUM(value), 0)) AS total_voucher,
       sum(case when is_used = 1 then value else 0 end) as total_used,
       sum(case when is_used = 1 then 0 else value end) as total_left
FROM voucher_history 
WHERE idUser = 1 AND DATE(FROM_UNIXTIME(datetime)) <= '2014-03-05';

您的查询存在问题，即它尝试在同一total_voucher语句中使用列别名（total_used和select）。 SQL不支持这一点。您需要使用子查询来获得该功能。

MySQL别名计算

1 个答案: