check this example
DECLARE @checkinout TABLE(in_time DATETIME, out_time DATETIME, senerio_id INT, u_id INT)
INSERT INTO @checkinout
SELECT * FROM
(
SELECT '2013-09-08 14:53' AS in_time, NULL AS out_time, 1 AS senerio_id, 1 AS u_id
UNION ALL
SELECT '2013-09-08 16:46' AS in_time, NULL AS out_time, 1 AS senerio_id, 2 AS u_id
UNION ALL
SELECT NULL AS in_time, '2013-09-08 15:53' AS out_time, 2 AS senerio_id, 1 AS u_id
UNION ALL
SELECT NULL AS in_time, '2013-09-08 16:53' AS out_time, 2 AS senerio_id, 2 AS u_id
) AS t
SELECT
u_id,
MAX(in_time) AS in_time,
MAX(out_time) AS out_time,
DATEDIFF(MI,MAX(in_time),
MAX(out_time)) AS diffInMinute
FROM @checkinout
GROUP BY u_id
Happy Coding!
:)