我有一个关于在 mysql 中使用条件查询表的问题。
我创建了一个这样的存储过程:
SELECT A.*, TIMESTAMPDIFF(SECOND,A.start, COALESCE(MIN(B.start), NOW())) AS timespent_in_sec FROM activity_logs A LEFT JOIN activity_logs B ON B.user_id = A.user_id AND B.id > A.id WHERE A.user_id = userId AND A.start >= startDate AND A.start <= endDate GROUP BY A.id, Day(A.start) ORDER BY A.start ASC
其中 userId、startDate 和 endDate 是一个参数。
所以当我执行下面的程序时,结果是:
id start activity user_id timespent_in_sec
--------------------------------------------------------------------------------
1 2018-11-12 10:37:53 Login 81 124
2 2018-11-12 10:39:57 1st Break 81 59
3 2018-11-12 10:40:56 1:1 Coaching 81 35
4 2018-11-12 10:41:31 2nd Break 81 76
5 2018-11-12 10:42:47 Logout 81 63384
所以我的目标是停止计算或在它们到达注销事件时将其设置为 0。像这样的事情:
id start activity user_id timespent_in_sec
1 2018-11-12 10:37:53 Login 81 124
2 2018-11-12 10:39:57 1st Break 81 59
3 2018-11-12 10:40:56 1:1 Coaching 81 35
4 2018-11-12 10:41:31 2nd Break 81 76
5 2018-11-12 10:42:47 Logout 81 0 // means user has been logout and this will end the computation od timespent in sec
感谢您的帮助。 提前致谢。
最佳答案
你可以尝试使用CASE WHEN
表达式。
SELECT A.*,
CASE WHEN activity = 'Logout'
THEN 0
ELSE TIMESTAMPDIFF(SECOND,A.start, COALESCE(MIN(B.start), NOW()))
END AS timespent_in_sec
FROM activity_logs A
LEFT JOIN activity_logs B ON B.user_id = A.user_id AND B.id > A.id
WHERE A.user_id = userId AND A.start >= startDate AND A.start <= endDate GROUP BY A.id, Day(A.start)
ORDER BY A.start ASC
关于MySQL 查询计算行之间的时间差,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53273847/