[LeetCode/Easy] 1141. User Activity for the Past 30 Days I

1. Input

1) Table: Activity (pk: 없음)

 

2. Output

1) 2019년 7월 27일까지의 30일동안 각 날짜마다 액티비티를 즐긴 사람들의 수를 출력

- 출력 순서는 상관 없다.

 

3. Example

 

4. Code

1) 첫 코드(2023/06/08)

select activity_date as day, count(user_id) as active_users
from (
    select user_id , activity_date
    from Activity
    where activity_date between '2019-06-28' and '2019-07-27'
    group by user_id, activity_date
) a
group by day;

- 33%