SQL Server 2014

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CREATE TABLE mytable(
   Empid      INTEGER  NOT NULL
  ,Department VARCHAR(2) NOT NULL
  ,Timestamp  DATETIME  NOT NULL
  ,Read_ID    INTEGER  NOT NULL
);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-29 11:12:00.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (5565,'IT','2017-01-29 12:28:06.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (5565,'IT','2017-01-29 12:28:07.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-29 13:12:00.000',2);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (5565,'IT','2017-01-29 13:28:06.000',2);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-30 07:42:15.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-30 16:16:15.000',2);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-31 09:05:00.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-31 11:05:00.000',2);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-31 13:20:00.000',1);
INSERT INTO mytable(Empid,Department,Timestamp,Read_ID) VALUES (3221,'IT','2017-01-31 16:10:00.000',2);
11 rows affected

select * from mytable order by empid, timestamp


Empid
Department
Timestamp
Read_ID


3221
IT
2017-01-29 11:12:00.000
1

3221
IT
2017-01-29 13:12:00.000
2

3221
IT
2017-01-30 07:42:15.000
1

3221
IT
2017-01-30 16:16:15.000
2

3221
IT
2017-01-31 09:05:00.000
1

3221
IT
2017-01-31 11:05:00.000
2

3221
IT
2017-01-31 13:20:00.000
1

3221
IT
2017-01-31 16:10:00.000
2

5565
IT
2017-01-29 12:28:06.000
1

5565
IT
2017-01-29 12:28:07.000
1

5565
IT
2017-01-29 13:28:06.000
2


SELECT
    t1.empid, 
    t1.department, 
    YEAR(t1.timestamp) Year,
    MONTH(t1.timestamp) Month,
    CONVERT(
        varchar(12), 
        DATEADD(minute, SUM(DATEDIFF(minute, t1.timestamp, t2.timestamp)), 0), 
        114
    ) TotalHours
FROM
    mytable t1
    INNER JOIN mytable t2 
        ON  t1.empid = t2.empid
        AND t2.read_id = 2
        AND t2.timestamp = (
            SELECT MIN(timestamp) 
            FROM mytable 
            WHERE 
                read_id = 2 
                AND empid = t2.empid 
                AND timestamp > t1.timestamp
        )
WHERE 
    t1.read_id = 1 
GROUP BY t1.empid, t1.department, YEAR(t1.timestamp), MONTH(t1.timestamp)
ORDER BY  1, 2, 3, 4


empid
department
Year
Month
TotalHours


3221
IT
2017
1
15:24:00:000

5565
IT
2017
1
02:00:00:000

Empid	Department	Timestamp	Read_ID
3221	IT	2017-01-29 11:12:00.000	1
3221	IT	2017-01-29 13:12:00.000	2
3221	IT	2017-01-30 07:42:15.000	1
3221	IT	2017-01-30 16:16:15.000	2
3221	IT	2017-01-31 09:05:00.000	1
3221	IT	2017-01-31 11:05:00.000	2
3221	IT	2017-01-31 13:20:00.000	1
3221	IT	2017-01-31 16:10:00.000	2
5565	IT	2017-01-29 12:28:06.000	1
5565	IT	2017-01-29 12:28:07.000	1
5565	IT	2017-01-29 13:28:06.000	2