[MYSQL] Easy Solution Using GROUP BY
\nSELECT\n    event_day AS day,\n    emp_id,\n    SUM(out_time-in_time) AS total_time\nFROM Employees\nGROUP BY emp_id, event_day\n
```\nSELECT\n    event_day AS day,\n    emp_id,\n    SUM(out_time-in_time) AS total_time\nFROM Employees\nGROUP BY emp_id, event_day\n```
['MySQL']