SQL Tutorials - Hopper Company Queries I - Part 27

Leetcode Question 1635
Hopper Company Queries I

Table: Drivers

+-------------+---------+
| Column Name | Type |
+-------------+---------+
| driver_id | int |
| join_date | date |
+-------------+---------+
driver_id is the primary key for this table.
Each row of this table contains the drivers ID and the date they joined the Hopper company.
Table: Rides

+--------------+---------+
| Column Name | Type |
+--------------+---------+
| ride_id | int |
| user_id | int |
| requested_at | date |
+--------------+---------+
ride_id is the primary key for this table.
Each row of this table contains the ID of a ride, the users ID that requested it, and the day they requested it.
There may be some ride requests in this table that were not accepted.
Table: AcceptedRides

+---------------+---------+
| Column Name | Type |
+---------------+---------+
| ride_id | int |
| driver_id | int |
| ride_distance | int |
| ride_duration | int |
+---------------+---------+
ride_id is the primary key for this table.
Each row of this table contains some information about an accepted ride.
It is guaranteed that each accepted ride exists in the Rides table.
Write an SQL query to report the following statistics for each month of 2020:

The number of drivers currently with the Hopper company by the end of the month (active_drivers).
The number of accepted rides in that month (accepted_rides).
Return the result table ordered by month in ascending order, where month is the month’s number (January is 1, February is 2, etc.).

The query result format is in the following example.

Drivers table:
+-----------+------------+
| driver_id | join_date |
+-----------+------------+
| 10 | 2019-12-10 |
| 8 | 2020-1-13 |
| 5 | 2020-2-16 |
| 7 | 2020-3-8 |
| 4 | 2020-5-17 |
| 1 | 2020-10-24 |
| 6 | 2021-1-5 |
+-----------+------------+

Rides table:
+---------+---------+--------------+
| ride_id | user_id | requested_at |
+---------+---------+--------------+
| 6 | 75 | 2019-12-9 |
| 1 | 54 | 2020-2-9 |
| 10 | 63 | 2020-3-4 |
| 19 | 39 | 2020-4-6 |
| 3 | 41 | 2020-6-3 |
| 13 | 52 | 2020-6-22 |
| 7 | 69 | 2020-7-16 |
| 17 | 70 | 2020-8-25 |
| 20 | 81 | 2020-11-2 |
| 5 | 57 | 2020-11-9 |
| 2 | 42 | 2020-12-9 |
| 11 | 68 | 2021-1-11 |
| 15 | 32 | 2021-1-17 |
| 12 | 11 | 2021-1-19 |
| 14 | 18 | 2021-1-27 |
+---------+---------+--------------+

AcceptedRides table:
+---------+-----------+---------------+---------------+
| ride_id | driver_id | ride_distance | ride_duration |
+---------+-----------+---------------+---------------+
| 10 | 10 | 63 | 38 |
| 13 | 10 | 73 | 96 |
| 7 | 8 | 100 | 28 |
| 17 | 7 | 119 | 68 |
| 20 | 1 | 121 | 92 |
| 5 | 7 | 42 | 101 |
| 2 | 4 | 6 | 38 |
| 11 | 8 | 37 | 43 |
| 15 | 8 | 108 | 82 |
| 12 | 8 | 38 | 34 |
| 14 | 1 | 90 | 74 |
+---------+-----------+---------------+---------------+

Result table:
+-------+----------------+----------------+
| month | active_drivers | accepted_rides |
+-------+----------------+----------------+
| 1 | 2 | 0 |
| 2 | 3 | 0 |
| 3 | 4 | 1 |
| 4 | 4 | 0 |
| 5 | 5 | 0 |
| 6 | 5 | 1 |
| 7 | 5 | 1 |
| 8 | 5 | 1 |
| 9 | 5 | 0 |
| 10 | 6 | 0 |
| 11 | 6 | 2 |
| 12 | 6 | 1 |
+-------+----------------+----------------+