task: #1141

Author: Ivanbyone

README.md

@@ -51,6 +51,7 @@ Have a good contributing!
     - [627. Swap Salary](./leetcode/easy/627.%20Swap%20Salary.sql)
     - [1068. Product Sales Analysis I](./leetcode/easy/1068.%20Product%20Sales%20Analysis%20I.sql)
     - [1075. Project Employees I](./leetcode/easy/1075.%20Project%20Employees%20I.sql)
+    - [1141. User Activity for the Past 30 Days I](./leetcode/easy/1141.%20User%20Activity%20for%20the%20Past%2030%20Days%20I.sql)
     - [1148. Article Views I](./leetcode/easy/1148.%20Article%20Views%20I.sql)
     - [1327. List the Products Ordered in a Period](./leetcode/easy/1327.%20List%20the%20Products%20Ordered%20in%20a%20Period.sql)
     - [1378. Replace Employee ID With The Unique Identifier](./leetcode/easy/1378.%20Replace%20Employee%20ID%20With%20The%20Unique%20Identifier.sql)

leetcode/easy/1141. User Activity for the Past 30 Days I.sql

@@ -0,0 +1,31 @@
+/*
+Question 1141. User Activity for the Past 30 Days I
+Link: https://leetcode.com/problems/user-activity-for-the-past-30-days-i/description/?envType=study-plan-v2&envId=top-sql-50
+
+Table: Activity
+
++---------------+---------+
+| Column Name   | Type    |
++---------------+---------+
+| user_id       | int     |
+| session_id    | int     |
+| activity_date | date    |
+| activity_type | enum    |
++---------------+---------+
+This table may have duplicate rows.
+The activity_type column is an ENUM (category) 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 a solution to find the daily active user count for a period of 30 days ending 2019-07-27 inclusively. A user was active on someday if they made at least one activity on that day.
+
+Return the result table in any order.
+*/
+
+SELECT 
+    activity_date AS day, --noqa: RF04
+    COUNT(DISTINCT user_id) AS active_users
+FROM Activity
+WHERE activity_date BETWEEN DATE '2019-07-27' - INTERVAL '29 days' AND DATE '2019-07-27'
+GROUP BY day