easiest group by and sum ()
\nselect event_day as day, emp_id, sum(out_time-in_time)as total_time \nfrom employees\ngroup by day,emp_id;\n
```\nselect event_day as day, emp_id, sum(out_time-in_time)as total_time \nfrom employees\ngroup by day,emp_id;\n```
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