CREATE TABLE time_table
(bank_id int,
 atm_id int,
 strt_date datetime,
 end_date datetime) 
 
 INSERT INTO time_table VALUES (1, 1, '2015/04/12 08:30' , '2015/04/12 09:15')
 INSERT INTO time_table VALUES (1, 2, '2015/04/12 09:00' , '2015/04/12 09:45')
 INSERT INTO time_table VALUES (1, 1, '2015/04/12 09:20' , '2015/04/12 09:55')
 
 INSERT INTO time_table VALUES (2, 1, '2015/04/12 09:20' , '2015/04/12 09:25')
 INSERT INTO time_table VALUES (2, 2, '2015/04/12 09:30' , '2015/04/12 09:55')
 INSERT INTO time_table VALUES (2, 1, '2015/04/12 10:30' , '2015/04/12 11:30')
 INSERT INTO time_table VALUES (2, 2, '2015/04/12 11:15' , '2015/04/12 11:55')
 
 INSERT INTO time_table VALUES (3, 1, '2015/04/12 08:00' , '2015/04/12 09:00')
 INSERT INTO time_table VALUES (3, 2, '2015/04/12 08:55' , '2015/04/12 09:20')
 INSERT INTO time_table VALUES (3, 1, '2015/04/12 09:15' , '2015/04/12 09:50')
 INSERT INTO time_table VALUES (3, 1, '2015/04/12 11:20' , '2015/04/12 12:15')
                          

-- part 1, create a view to identify the contiguousy
 CREATE VIEW contiguous_vu
 AS
 SELECT bank_id, strt_date, 
              ISNULL(end_date, '9999-12-31') end_date,
              CASE
              WHEN strt_date > MAX(ISNULL(end_date, '9999-12-31'))
                               over(PARTITION BY bank_id ORDER BY strt_date 
                                    ROWS BETWEEN UNBOUNDED PRECEDING
                                    AND 1 preceding)
              THEN 1
              END contiguous_identifier
              FROM time_table
-- part 2, group the different parts 
SELECT bank_id, MIN(strt_date), MAX(end_date)
FROM
    (   SELECT  bank_id, strt_date, end_date, contiguous_identifier ,
        SUM(contiguous_identifier) over(PARTITION BY bank_id ORDER BY strt_date) contiguousy
        FROM contiguous_vu
    )   TAB 
GROUP BY bank_id, contiguousy
ORDER BY 1, 2