LeetCode 1741. Find Total Time Spent by Each Employee

問題：計算每一天不同員工進出時間

解法：透過SUM計算進出時間，Group BY將emp_id和event_day分組

SELECT event_day as day, emp_id, SUM(out_time - in_time) as total_time
FROM Employees
GROUP BY emp_id, event_day
ORDER BY event_day;