MySQL 8.0

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select version();


version()


8.0.27


CREATE TABLE record (
    eventDate date,
    event VARCHAR(100),
    eventStart TIMESTAMP,
    eventEnd TIMESTAMP,
    durations double
);

INSERT INTO record VALUES 
( '2020-02-01' , 'eventB', '2020-02-01 09:10:25', '2020-02-01 09:50:25', 40.0 ),
( '2020-02-01' , 'eventD', '2020-02-01 09:15:25', '2020-02-01 09:20:25', 5.0),
( '2020-02-01' , 'eventC', '2020-02-01 09:30:25', '2020-02-01 09:35:25', 5.0),
( '2020-02-01' , 'eventD', '2020-02-01 09:40:25', '2020-02-01 09:45:25', 5.0),
( '2020-02-01' , 'eventC', '2020-02-01 09:55:25', '2020-02-01 09:59:25', 4.0);

SELECT * FROM record;


eventDate
event
eventStart
eventEnd
durations


2020-02-01
eventB
2020-02-01 09:10:25
2020-02-01 09:50:25
40

2020-02-01
eventD
2020-02-01 09:15:25
2020-02-01 09:20:25
5

2020-02-01
eventC
2020-02-01 09:30:25
2020-02-01 09:35:25
5

2020-02-01
eventD
2020-02-01 09:40:25
2020-02-01 09:45:25
5

2020-02-01
eventC
2020-02-01 09:55:25
2020-02-01 09:59:25
4


WITH RECURSIVE
-- enumerate rows within the date ordering by event start
cte1 AS ( SELECT eventDate,
                 eventStart,
                 eventEnd,
                 ROW_NUMBER() OVER (PARTITION BY eventDate ORDER BY eventStart) rn
          FROM record
),
-- process rows, combine previous and current ranges into one range
cte2 AS ( SELECT eventDate,
                 rn, 
                 eventStart xstart, 
                 eventEnd xend
          FROM cte1 
          WHERE rn = 1
          UNION ALL
          SELECT cte1.eventDate,
                 cte1.rn,
                 CASE WHEN cte2.xend < cte1.eventStart
                      THEN cte1.eventStart
                      ELSE cte2.xstart
                      END,
                 GREATEST(cte1.eventEnd, cte2.xend)
          FROM cte2
          JOIN cte1 ON cte1.rn = cte2.rn + 1
                   AND cte1.eventDate = cte2.eventDate
),
-- remove intermediate ranges
cte3 AS ( SELECT eventDate, xstart, MAX(xend) xend
          FROM cte2
          GROUP BY 1, 2
)
-- get needed data
SELECT eventDate,
       SUM(TIMESTAMPDIFF(MINUTE, xstart, xend)) duration
FROM cte3
GROUP BY 1


eventDate
duration


2020-02-01
44

eventDate	event	eventStart	eventEnd	durations
2020-02-01	eventB	2020-02-01 09:10:25	2020-02-01 09:50:25	40
2020-02-01	eventD	2020-02-01 09:15:25	2020-02-01 09:20:25	5
2020-02-01	eventC	2020-02-01 09:30:25	2020-02-01 09:35:25	5
2020-02-01	eventD	2020-02-01 09:40:25	2020-02-01 09:45:25	5
2020-02-01	eventC	2020-02-01 09:55:25	2020-02-01 09:59:25	4