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hopper-company-queries-i.sql
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hopper-company-queries-i.sql
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/*
Hopper Company Queries I Problem
Description
LeetCode Problem 1635.
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 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 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 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 |
+-------+----------------+----------------+
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 Septemeber --> 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).
*/
# V0
# V1
# https://circlecoder.com/hopper-company-queries-I/
select t.month,
count(distinct driver_id) active_drivers,
count(distinct rides.ride_id) accepted_rides
from
((select 1 as month)
union (select 2 as month)
union (select 3 as month)
union (select 4 as month)
union (select 5 as month)
union (select 6 as month)
union (select 7 as month)
union (select 8 as month)
union (select 9 as month)
union (select 10 as month)
union (select 11 as month)
union (select 12 as month)) t
left join
(select driver_id,
(case when year(join_date) = 2019 then '1' else month(join_date) end) `month`
from Drivers
where year(join_date) <= 2020) d
on d.month <= t.month
left join
(select month(requested_at) as `month`, a.ride_id
from AcceptedRides a
join Rides r
on r.ride_id = a.ride_id
where year(requested_at) = 2020) rides
on t.month = rides.month
group by t.month
order by t.month
# V2
# Time: O(d + r + tlogt)
# Space: O(d + r + t)
WITH RECURSIVE year_cte AS (
SELECT MIN(YEAR(join_date)) year,
MAX(YEAR(join_date)) max_year
FROM drivers
UNION ALL
SELECT year + 1,
max_year
FROM year_cte
WHERE year < max_year
),
year_month_cte AS (
SELECT year,
1 month,
12 max_month
FROM year_cte
UNION ALL
SELECT year,
month + 1,
max_month
FROM year_month_cte
WHERE month < max_month
),
drivers_count_cte AS(
SELECT MAX(YEAR(d.join_date)) 'year',
MAX(MONTH(d.join_date)) 'month',
COUNT(d.driver_id) drivers_count
FROM drivers d
GROUP BY LEFT(d.join_date, 7)
),
rides_count_cte AS (
SELECT MAX(YEAR(r.requested_at)) 'year',
MAX(MONTH(r.requested_at)) 'month',
COUNT(a.ride_id) accepted_rides
FROM rides r LEFT JOIN acceptedrides a ON r.ride_id = a.ride_id
GROUP BY LEFT(r.requested_at, 7)
)
SELECT month,
active_drivers,
accepted_rides
FROM (
SELECT t1.month,
t1.year,
IFNULL(SUM(t2.drivers_count) OVER (ORDER BY t1.year, t1.month), 0) active_drivers,
IFNULL(t3.accepted_rides, 0) accepted_rides
FROM year_month_cte t1
LEFT JOIN drivers_count_cte t2 ON t1.year = t2.year AND t1.month = t2.month
LEFT JOIN rides_count_cte t3 ON t1.year = t3.year AND t1.month = t3.month
) tmp
WHERE year = 2020;