SQL time difference within single table

Question

I have a single MySQL table with login data of users.

user |  date               | type
-----+---------------------+------
1    | 2011-01-05 08:00:00 | login         


        

Answer 1

SELECT x.*, TIMEDIFF(x.logout_date, x.login_date) as duration
FROM
(
SELECT a.user_id, a.`date` as logout_date, 
(SELECT MAX(b.`date`) FROM table1 b WHERE b.`date` <a.`date` 
and b.user=a.user and b.type = 'login') as login_date    
FROM table1 a WHERE a.type ='logout'
)x