Description
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 compute the average_ride_distance and average_ride_duration of every 3-month window starting from January - March 2020 to October - December 2020. Round average_ride_distance and average_ride_duration to the nearest two decimal places.
The average_ride_distance is calculated by summing up the total ride_distance values from the three months and dividing it by 3. The average_ride_duration is calculated in a similar way.
Return the result table ordered by month in ascending order, where month is the starting month’s number (January is 1, February is 2, etc.).
SQL Schema
Create table If Not Exists Drivers (driver_id int, join_date date)
Create table If Not Exists Rides (ride_id int, user_id int, requested_at date)
Create table If Not Exists AcceptedRides (ride_id int, driver_id int, ride_distance int, ride_duration int)
Truncate table Drivers
insert into Drivers (driver_id, join_date) values ('10', '2019-12-10')
insert into Drivers (driver_id, join_date) values ('8', '2020-1-13')
insert into Drivers (driver_id, join_date) values ('5', '2020-2-16')
insert into Drivers (driver_id, join_date) values ('7', '2020-3-8')
insert into Drivers (driver_id, join_date) values ('4', '2020-5-17')
insert into Drivers (driver_id, join_date) values ('1', '2020-10-24')
insert into Drivers (driver_id, join_date) values ('6', '2021-1-5')
Truncate table Rides
insert into Rides (ride_id, user_id, requested_at) values ('6', '75', '2019-12-9')
insert into Rides (ride_id, user_id, requested_at) values ('1', '54', '2020-2-9')
insert into Rides (ride_id, user_id, requested_at) values ('10', '63', '2020-3-4')
insert into Rides (ride_id, user_id, requested_at) values ('19', '39', '2020-4-6')
insert into Rides (ride_id, user_id, requested_at) values ('3', '41', '2020-6-3')
insert into Rides (ride_id, user_id, requested_at) values ('13', '52', '2020-6-22')
insert into Rides (ride_id, user_id, requested_at) values ('7', '69', '2020-7-16')
insert into Rides (ride_id, user_id, requested_at) values ('17', '70', '2020-8-25')
insert into Rides (ride_id, user_id, requested_at) values ('20', '81', '2020-11-2')
insert into Rides (ride_id, user_id, requested_at) values ('5', '57', '2020-11-9')
insert into Rides (ride_id, user_id, requested_at) values ('2', '42', '2020-12-9')
insert into Rides (ride_id, user_id, requested_at) values ('11', '68', '2021-1-11')
insert into Rides (ride_id, user_id, requested_at) values ('15', '32', '2021-1-17')
insert into Rides (ride_id, user_id, requested_at) values ('12', '11', '2021-1-19')
insert into Rides (ride_id, user_id, requested_at) values ('14', '18', '2021-1-27')
Truncate table AcceptedRides
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('10', '10', '63', '38')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('13', '10', '73', '96')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('7', '8', '100', '28')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('17', '7', '119', '68')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('20', '1', '121', '92')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('5', '7', '42', '101')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('2', '4', '6', '38')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('11', '8', '37', '43')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('15', '8', '108', '82')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('12', '8', '38', '34')
insert into AcceptedRides (ride_id, driver_id, ride_distance, ride_duration) values ('14', '1', '90', '74')
Idea
The query result format is in the following example.
+-------+-----------------------+-----------------------+
| month | average_ride_distance | average_ride_duration |
+-------+-----------------------+-----------------------+
| 1 | 21.00 | 12.67 |
| 2 | 21.00 | 12.67 |
| 3 | 21.00 | 12.67 |
| 4 | 24.33 | 32.00 |
| 5 | 57.67 | 41.33 |
| 6 | 97.33 | 64.00 |
| 7 | 73.00 | 32.00 |
| 8 | 39.67 | 22.67 |
| 9 | 54.33 | 64.33 |
| 10 | 56.33 | 77.00 |
+-------+-----------------------+-----------------------+
Fulfill requirements :
Before all, I would like to share a problem for timeout limit exceeded of this question when I submit my solution. Because of the pervious solution, I used subquery in select column statement to calculate average distance and average duration.
So, I’m learned when the query statement meet a large dataset, the subquery will spending more process resource to calculate its.
For the above reason, I modifying the output query used function lead() getting next two months distance and duration for each row instead of subquery. From the response of submissions, it’s worked and improve the query performance.
Solution
with
cte_month as (
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
),
cte_accepted_rides as (
select
c.month,
sum(c.distance) as distance,
sum(c.duration) as duration
from (
select
month(b.requested_at) as month,
a.ride_distance as distance,
a.ride_duration as duration
from AcceptedRides a
join Rides b using(ride_id)
where year(b.requested_at) = 2020
) c
group by c.month
),
cte_ride_info as (
select
a.month,
ifnull(b.distance, 0) as m0_distance,
ifnull(b.duration, 0) as m0_duration,
ifnull(lead(b.distance, 1) over(order by a.month), 0) as m1_distance,
ifnull(lead(b.duration, 1) over(order by a.month), 0) as m1_duration,
ifnull(lead(b.distance, 2) over(order by a.month), 0) as m2_distance,
ifnull(lead(b.duration, 2) over(order by a.month), 0) as m2_duration
from cte_month a
left join cte_accepted_rides b on b.month = a.month
)
select
distinct(a.month),
round((m0_distance + m1_distance + m2_distance ) / 3, 2) as average_ride_distance,
round((m0_duration + m1_duration + m2_duration ) / 3, 2) as average_ride_duration
from cte_ride_info a
where a.month <= 10