题解 | #牛客每个人最近的登录日期(二)#

SELECT
    u_name,
    c_name,
    max( date ) 
FROM
    (
SELECT 
    user.NAME AS u_name,
    user_id,
    login.client_id,
    client.NAME AS c_name,
    date 
FROM
    login
    LEFT JOIN user ON login.user_id = user.id
    LEFT JOIN client ON login.client_id = client.id 
ORDER BY
    date DESC 
    LIMIT 10000000 
    ) AS tb1 
GROUP BY
    user_id
ORDER BY
    u_name

遇到几次这样的问题了记录一下：group by与max（列名）取最值对应行的数据时，除max字段外，其余字段均为默认的首行数据。应在分组前对其进行排序，且必须加limit进行限制使排序操作生效。(https://blog.csdn.net/liangwenrong/article/details/118307048)