Question

以下查询中有group by子句错误。我不知道如何使它正确

SELECT user_id, MAX(updated_date), DATEDIFF(NOW(),MAX(updated_date))
FROM `authentication`
WHERE DATEDIFF(NOW(),MAX(updated_date)) > 20
GROUP by user_id

Answer 1

大概您想要一个having子句：

SELECT user_id, MAX(updated_date), 
       DATEDIFF(NOW(), MAX(updated_date)) as diff
FROM `authentication`
GROUP by user_id
HAVING diff > 20

Answer 2

无需在MAX()子句中进行WHERE：

SELECT user_id, MAX(updated_date), DATEDIFF(NOW(),MAX(updated_date))
FROM `authentication`
WHERE DATEDIFF(NOW(),updated_date) > 20
GROUP by user_id

Answer 3

为了提高性能，请使用进一步修改其他答案之一

WHERE updated_date > CURDATE() - INTERVAL 20 DAY

和索引updated_date。

在where子句中使用max的日期差异

3 个答案: