total_time that stores the difference between out_time and in_time for each entry.event_day and emp_id.total_time for each group to get the total time spent by each employee on each day.event_day column to day and ensure it is of type string if necessary.day, emp_id, and total_time.erDiagram
Employees {
int emp_id
date event_day
int in_time
int out_time
emp_id event_day in_time PK
}