前述

mysql中date_add()函数的使用

题目描述

leetcode题目：1141. 查询近30天活跃用户数

Code

写法一

select activity_date as day, count(distinct user_id) as active_users
from Activity
where activity_date > '2019-06-27' and activity_date <= '2019-07-27'
group by activity_date

注意：where activity_date between '2019-06-27' and '2019-07-27' ERROR: 不包含’2019-06-27’

写法二： date_add()

select activity_date as day, count(distinct user_id) as active_users
from Activity
where activity_date between date_add('2019-07-27', interval -29 day) and '2019-07-27'
group by activity_date

学习题解中的用date_add()函数：（新手）关于使用DATE_ADD简化“近30天”的思路