MySQL 8.0

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CREATE TABLE document (
  process_id           INT,
  process_start        TIMESTAMP,
  process_end          TIMESTAMP,
  data_1               VARCHAR(32),
  data_2               INT
);
INSERT INTO document SELECT 1, '2017-12-05 15:21:55', '2017-12-05 15:13:49', 'a', 1;
INSERT INTO document SELECT 2, '2017-12-05 15:40:19', '2017-12-05 21:56:10', 'b', 2;
INSERT INTO document SELECT 3, '2017-12-05 21:18:10', '2017-12-05 22:04:46', 'c', 3;
INSERT INTO document SELECT 4, '2017-12-05 22:05:50', '2017-12-05 22:08:11', 'b', 4;
CREATE TABLE numbers (
  id   INT
);
INSERT INTO numbers SELECT 0;
INSERT INTO numbers SELECT 1;
INSERT INTO numbers SELECT 2 + id FROM numbers;
INSERT INTO numbers SELECT 4 + id FROM numbers;
INSERT INTO numbers SELECT 8 + id FROM numbers;
SELECT
  rounded.process_id,
  rounded.process_start,
  rounded.process_end,
  TIMESTAMPADD(HOUR, numbers.id, rounded.process_start_hour)   AS process_hour,
  rounded.data_1,
  rounded.data_2
FROM
(
  SELECT
    *,
    DATE_FORMAT(process_start,'%Y-%m-%d %H:00:00')   process_start_hour,
    DATE_FORMAT(process_end  ,'%Y-%m-%d %H:00:00')   process_end_hour
  FROM
    document
)
  rounded
INNER JOIN
  numbers
    ON numbers.id <= EXTRACT(HOUR FROM TIMEDIFF(process_end_hour, process_start_hour))
ORDER BY
  rounded.process_id,
  numbers.id


process_id
process_start
process_end
process_hour
data_1
data_2


1
2017-12-05 15:21:55
2017-12-05 15:13:49
2017-12-05 15:00:00
a
1

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 15:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 16:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 17:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 18:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 19:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 20:00:00
b
2

2
2017-12-05 15:40:19
2017-12-05 21:56:10
2017-12-05 21:00:00
b
2

3
2017-12-05 21:18:10
2017-12-05 22:04:46
2017-12-05 21:00:00
c
3

3
2017-12-05 21:18:10
2017-12-05 22:04:46
2017-12-05 22:00:00
c
3

4
2017-12-05 22:05:50
2017-12-05 22:08:11
2017-12-05 22:00:00
b
4

process_id	process_start	process_end	process_hour	data_1	data_2
1	2017-12-05 15:21:55	2017-12-05 15:13:49	2017-12-05 15:00:00	a	1
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 15:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 16:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 17:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 18:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 19:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 20:00:00	b	2
2	2017-12-05 15:40:19	2017-12-05 21:56:10	2017-12-05 21:00:00	b	2
3	2017-12-05 21:18:10	2017-12-05 22:04:46	2017-12-05 21:00:00	c	3
3	2017-12-05 21:18:10	2017-12-05 22:04:46	2017-12-05 22:00:00	c	3
4	2017-12-05 22:05:50	2017-12-05 22:08:11	2017-12-05 22:00:00	b	4