枚举类型和MySQL

Question

我的任务很简单，我陷入了困境。 我有表login_history

`login_history_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`login_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`login_action` enum('login','logout') NOT NULL,
`user_id` int(11) unsigned NOT NULL, (this one is foreign key)

任务：编写一个查询，该查询将找到一个在2012年9月星期三注销次数最多的用户。

如您所见，我有enum类型的login_action，并且我需要找到某个特定日期某用户的注销次数最多。.这是我到目前为止所做的，我只需要一点点正确的方向，有人就可以告诉我我在哪里在这里错了..

SELECT fullname FROM user WHERE user_id = (
SELECT user_id FROM login_history WHERE (user_id,login_action) = (
    SELECT user_id, COUNT(login_action) FROM login_history WHERE login_action = 'logout' AND login_time = (
        SELECT login_time FROM login_history WHERE YEAR(login_time) = 2012 AND MONTH(login_time) = 9 AND DAYOFWEEK(login_time) = 3)));

Answer 1

尝试这个：

select u.fullname from (select count(*) n,user_id 
from login_history where 
login_time between '2012-09-01' and '2012-10-01' and dayofweek(login_time) = 3 and login_action = 'logout'
group by user_id order by n desc limit 1) a, user u where a.user_id = u.user_id

为了获得良好的性能，请确保在login_time列上具有键。