力扣高频SQL 50题（基础版）第二十一题之1141.查询近30天活跃用户数

力扣高频SQL 50题（基础版）第二十一题

1141.查询近30天活跃用户数

题目说明

表：Activity

±--------------±--------+

| Column Name | Type |

±--------------±--------+

| user_id | int |

| session_id | int |

| activity_date | date |

| activity_type | enum |

±--------------±--------+

该表没有包含重复数据。

activity_type 列是 ENUM(category) 类型， 从 (‘open_session’， ‘end_session’， ‘scroll_down’， ‘send_message’) 取值。

该表记录社交媒体网站的用户活动。

注意，每个会话只属于一个用户。

编写解决方案，统计截至 2019-07-27（包含2019-07-27），近 30 天的每日活跃用户数（当天只要有一条活动记录，即为活跃用户）。

以 任意顺序 返回结果表。

思路分析

实现过程

准备数据

Create table If Not Exists Activity (user_id int, session_id int, activity_date date, activity_type ENUM('open_session', 'end_session', 'scroll_down', 'send_message'))
Truncate table Activity
insert into Activity (user_id, session_id, activity_date, activity_type) values ('1', '1', '2019-07-20', 'open_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('1', '1', '2019-07-20', 'scroll_down')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('1', '1', '2019-07-20', 'end_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('2', '4', '2019-07-20', 'open_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('2', '4', '2019-07-21', 'send_message')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('2', '4', '2019-07-21', 'end_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('3', '2', '2019-07-21', 'open_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('3', '2', '2019-07-21', 'send_message')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('3', '2', '2019-07-21', 'end_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('4', '3', '2019-06-25', 'open_session')
insert into Activity (user_id, session_id, activity_date, activity_type) values ('4', '3', '2019-06-25', 'end_session')

实现方式

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

结果截图