문제
정답
SELECT user_id, MAX(time_stamp) AS last_stamp
FROM Logins
WHERE time_stamp >= '2020-01-01' AND time_stamp < '2021-01-01'
GROUP BY user_id
SELECT user_id, MAX(time_stamp) AS last_stamp
FROM Logins
WHERE time_stamp >= '2020-01-01' AND time_stamp < '2021-01-01'
GROUP BY user_id