如何在使用MySQL的別名列上選擇使用WHERE條件？

Question

我有以下查詢：

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

我怎麼只返回有'no'行？

Answer 1

添加WHERE條件。 您不能在條款上使用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' 

或使用子查詢

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

我相信你可以做這樣的事情

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

FROM users_codes 
HAVING Expired = 'no';