枚舉類型和MySQL

Question

我的任務很簡單，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)

任務：編寫一個查詢，該查詢將找到一個在2012年9月星期三注銷次數最多的用戶。

如您所見，我有enum類型的login_action，並且我需要找到某個特定日期某用戶的注銷次數最多。.這是我到目前為止所做的，我只需要一點點正確的方向，有人就可以告訴我我在哪里在這里錯了..

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

嘗試這個：

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

為了獲得良好的性能，請確保在login_time列上具有鍵。