SQL query to find the time difference - sql

Question

I want to find the time difference between the login and logout of a user.
The hard part for me is that both login and logout time is in one column and there is a "Status" column to show if it is login/logout.
Example:
Timestamp Status UserName
2015-04-26 20:12:33 Login Grashia
2015-04-26 23:22:13 Logout Grashia
How do I query this?
I tried the DATEDIFF function but I know thats not the right way.

Answer 1

Suppose you have the following table schema
CREATE TABLE `user_log` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`dt` datetime DEFAULT NULL,
`status` varchar(15) COLLATE utf8_bin DEFAULT NULL,
PRIMARY KEY (`id`)
);
with this sort of data
+----+---------+---------------------+--------+
| id | user_id | dt | status |
+----+---------+---------------------+--------+
| 1 | 1 | 2015-09-23 08:35:36 | Login |
| 2 | 1 | 2015-09-23 17:15:44 | Logout |
| 3 | 1 | 2015-09-24 08:55:18 | Login |
| 4 | 2 | 2015-09-23 09:00:16 | Login |
| 5 | 2 | 2015-09-23 18:00:23 | Logout |
+----+---------+---------------------+--------+
You can use this query
SELECT i.user_id, i.dt AS 'login_dt', IFNULL(o.dt, '-') AS 'logout_dt',
TIMEDIFF(IFNULL(o.dt, NOW()), i.dt) AS 'total_time'
FROM
(SELECT * FROM user_log WHERE `status`='Login') i
LEFT OUTER JOIN (SELECT * FROM user_log WHERE `status`='Logout') o
ON i.user_id=o.user_id AND DATE(i.dt)=DATE(o.dt)
to get this result
+---------+---------------------+---------------------+------------+
| user_id | login_dt | logout_dt | total_time |
+---------+---------------------+---------------------+------------+
| 1 | 2015-09-23 08:35:36 | 2015-09-23 17:15:44 | 08:40:08 |
| 1 | 2015-09-24 08:55:18 | - | 00:10:23 |
| 2 | 2015-09-23 09:00:16 | 2015-09-23 18:00:23 | 09:00:07 |
+---------+---------------------+---------------------+------------+
You have to add required indices and set proper table engine for optimum performance

Answer 2

if it is SQL server your query will look like this:
I suppose that there should be a column userid:
You need to join two table to make compare data in the same column
SELECT in. username, DATEDIFF(minute, in.timestamp, out.timestamp)
FROM
(SELECT username, timestamp FROM logtable WHERE status = 'Login') as IN
INNER JOIN
(SELECT username, timestamp FROM logtable WHERE status = 'logout') AS OUT
ON in.userid = out.useriD
you can read more about DATEDIFF function here:
https://msdn.microsoft.com/en-us/library/ms189794.aspx