如何使用MySQL在别名列上使用WHERE条件进行选择？

Question

我有以下查询：

SELECT IF(TIMESTAMPDIFF(HOUR,users_codes.timestam,CURRENT_TIMESTAMP()) < 48,'no','yes') AS Expired
FROM users_codes

如何仅返回'no'？

的行

Answer 1

添加WHERE条件。 您不能在where子句上使用ALIAS。

SELECT IF(TIMESTAMPDIFF(HOUR,users_codes.timestam,CURRENT_TIMESTAMP()) < 48,'no','yes') AS Expired 
FROM   users_codes
WHERE  IF(TIMESTAMPDIFF(HOUR,users_codes.timestam,CURRENT_TIMESTAMP()) < 48,'no','yes') = 'no'

或使用子查询

SELECT *
FROM
(
    SELECT IF(TIMESTAMPDIFF(HOUR,users_codes.timestam,CURRENT_TIMESTAMP()) < 48,'no','yes') AS Expired 
    FROM   users_codes
) s
WHERE  Expired  = 'no'

Answer 2

我相信你可以做这样的事情

SELECT IF( TIMESTAMPDIFF(
    HOUR,
    users_codes.timestam,
    CURRENT_TIMESTAMP()
  ) < 48, 'no', 'yes') AS Expired

FROM users_codes
HAVING Expired = 'no';