refactor 1141

fishercoder1534 · fishercoder1534 · commit 836b95c68f6a · 2020-04-25T13:52:33.000-07:00
diff --git a/database/_1141.sql b/database/_1141.sql
@@ -1,52 +1,3 @@
---1141. User Activity for the Past 30 Days I
---
---Table: Activity
---
---+---------------+---------+
---| Column Name   | Type    |
---+---------------+---------+
---| user_id       | int     |
---| session_id    | int     |
---| activity_date | date    |
---| activity_type | enum    |
---+---------------+---------+
---There is no primary key for this table, it may have duplicate rows.
---The activity_type column is an ENUM of type ('open_session', 'end_session', 'scroll_down', 'send_message').
---The table shows the user activities for a social media website.
---Note that each session belongs to exactly one user.
---
---
---Write an SQL query to find the daily active user count for a period of 30 days ending 2019-07-27 inclusively. A user was active on some day if he/she made at least one activity on that day.
---
---The query result format is in the following example:
---
---Activity table:
---+---------+------------+---------------+---------------+
---| user_id | session_id | activity_date | activity_type |
---+---------+------------+---------------+---------------+
---| 1       | 1          | 2019-07-20    | open_session  |
---| 1       | 1          | 2019-07-20    | scroll_down   |
---| 1       | 1          | 2019-07-20    | end_session   |
---| 2       | 4          | 2019-07-20    | open_session  |
---| 2       | 4          | 2019-07-21    | send_message  |
---| 2       | 4          | 2019-07-21    | end_session   |
---| 3       | 2          | 2019-07-21    | open_session  |
---| 3       | 2          | 2019-07-21    | send_message  |
---| 3       | 2          | 2019-07-21    | end_session   |
---| 4       | 3          | 2019-06-25    | open_session  |
---| 4       | 3          | 2019-06-25    | end_session   |
---+---------+------------+---------------+---------------+
---
---Result table:
---+------------+--------------+
---| day        | active_users |
---+------------+--------------+
---| 2019-07-20 | 2            |
---| 2019-07-21 | 2            |
---+------------+--------------+
---Note that we do not care about days with zero active users.
-
---# Write your MySQL query statement below
 select activity_date as day, count(distinct(user_id)) as active_users from Activity
 where activity_date between "2019-06-28" and "2019-07-27"
 group by activity_date;
