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1635. Hopper Company Queries I
Description
Table: Drivers
+-------------+---------+ | Column Name | Type | +-------------+---------+ | driver_id | int | | join_date | date | +-------------+---------+ driver_id is the primary key (column with unique values) for this table. Each row of this table contains the driver's 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 (column with unique values) for this table. Each row of this table contains the ID of a ride, the user's 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 (column with unique values) 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 a solution 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 result format is in the following example.
Example 1:
Input: 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 | +---------+-----------+---------------+---------------+ Output: +-------+----------------+----------------+ | 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 | +-------+----------------+----------------+ Explanation: By the end of January --> two active drivers (10, 8) and no accepted rides. By the end of February --> three active drivers (10, 8, 5) and no accepted rides. By the end of March --> four active drivers (10, 8, 5, 7) and one accepted ride (10). By the end of April --> four active drivers (10, 8, 5, 7) and no accepted rides. By the end of May --> five active drivers (10, 8, 5, 7, 4) and no accepted rides. By the end of June --> five active drivers (10, 8, 5, 7, 4) and one accepted ride (13). By the end of July --> five active drivers (10, 8, 5, 7, 4) and one accepted ride (7). By the end of August --> five active drivers (10, 8, 5, 7, 4) and one accepted ride (17). By the end of September --> five active drivers (10, 8, 5, 7, 4) and no accepted rides. By the end of October --> six active drivers (10, 8, 5, 7, 4, 1) and no accepted rides. By the end of November --> six active drivers (10, 8, 5, 7, 4, 1) and two accepted rides (20, 5). By the end of December --> six active drivers (10, 8, 5, 7, 4, 1) and one accepted ride (2).
Solutions
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# Write your MySQL query statement below WITH recursive Months AS ( SELECT 1 AS month UNION ALL SELECT month + 1 FROM Months WHERE month < 12 ), Ride AS ( SELECT MONTH(requested_at) AS month, COUNT(1) AS cnt FROM Rides AS r JOIN AcceptedRides AS a ON r.ride_id = a.ride_id AND YEAR(requested_at) = 2020 GROUP BY month ) SELECT m.month, COUNT(driver_id) AS active_drivers, IFNULL(r.cnt, 0) AS accepted_rides FROM Months AS m LEFT JOIN Drivers AS d ON (m.month >= MONTH(d.join_date) AND YEAR(d.join_date) = 2020) OR YEAR(d.join_date) < 2020 LEFT JOIN Ride AS r ON m.month = r.month GROUP BY month;