1141. User Activity for the Past 30 Days I : leetcode

# INTERVAL 30 days
SELECT  activity_date as day,
        count(user_id) as active_users
FROM    Activity
WHERE   activity_date BETWEEN ('2019-07-27' INTERVAL 30 DAY) AND '2019-07-27'
GROUP BY
        activity_date

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INTERVAL 30 DAY) AND '2019-07-27'
GROUP BY
activity_date' at line 5
에러 원인 : INTERVAL을 사용하는데 DATE 관련 함수를 안 썼다.

# INTERVAL 30 days
SELECT  activity_date as day,
        count(DISTINCT user_id) as active_users
FROM    Activity
WHERE   activity_date BETWEEN DATE_SUB('2019-07-27', INTERVAL 29 DAY) AND '2019-07-27'
GROUP BY
        activity_date