SQL - GROUP BY
SELECT event_day day, emp_id, sum(out_time-in_time) total_time \nFROM Employees\nGROUP BY event_day,emp_id;
``SELECT event_day day, emp_id, sum(out_time-in_time) total_time \nFROM Employees\nGROUP BY event_day,emp_id;``
['MySQL']