# Calculate Ride Cancellation Rate using SQL

Calculating Ride Cancellation Rate is a popular SQL question in Data Science interviews. It involves analyzing the cancellation rate for ride requests, specifically from users who are not banned. So, if you want to know how to calculate the ride cancellation rate, this article is for you. In this article, I will take you through how to calculate the ride cancellation rate using SQL.

## Calculate Ride Cancellation Rate: Problem Statement

Given two tables, “Trips” and “Users”, containing information on trips and users respectively. Calculate the cancellation rate for carpool requests involving users who are not banned. A ride request is considered cancelled if it is cancelled either by the customer or by the driver. The cancellation rate is calculated by dividing the number of cancelled requests (involving non-banned users) by the total number of requests (with non-banned users) each day.

Input Tables:

```Trips:
+------+-----------+-----------+---------+---------------------+------------+
| id   | client_id | driver_id | city_id | status              | request_at |
+------+-----------+-----------+---------+---------------------+------------+
|    1 |         1 |        10 |       1 | completed           | 2023-07-12 |
|    2 |         2 |        11 |       1 | cancelled_by_driver | 2023-07-12 |
|    3 |         3 |        12 |       6 | completed           | 2023-07-12 |
|    4 |         4 |        13 |       6 | cancelled_by_client | 2023-07-12 |
|    5 |         1 |        10 |       1 | completed           | 2023-07-13 |
|    6 |         2 |        11 |       6 | completed           | 2023-07-13 |
|    7 |         3 |        12 |       6 | completed           | 2023-07-13 |
|    8 |         2 |        12 |      12 | completed           | 2023-07-14 |
|    9 |         3 |        10 |      12 | completed           | 2023-07-14 |
|   10 |         4 |        13 |      12 | cancelled_by_driver | 2023-07-14 |
+------+-----------+-----------+---------+---------------------+------------+

Users:
+----------+--------+--------+
| users_id | banned | role   |
+----------+--------+--------+
|        1 | No     | client |
|        2 | Yes    | client |
|        3 | No     | client |
|        4 | No     | client |
|       10 | No     | driver |
|       11 | No     | driver |
|       12 | No     | driver |
|       13 | No     | driver |
+----------+--------+--------+```

## Calculate Ride Cancellation Rate using SQL

The “Trips” table includes details such as trip ID, rider ID, driver ID, city ID, status, and request date. The “Users” table contains user information such as user ID, ban status, and role. To solve this problem, we can join the “Trips” and “Users” tables based on the rider ID and driver ID, ensuring both the client and driver are not banned. By applying this filter, we can focus specifically on ride requests involving unbanned users.

Next, we need to group the data by request date and calculate the number of cancelled requests and the total number of requests for each day.

First, let’s create the input tables for our SQL database (I am using MySql):

```CREATE TABLE Trips (
id INT,
client_id INT,
driver_id INT,
city_id INT,
status VARCHAR(20),
request_at DATE
);

INSERT INTO Trips (id, client_id, driver_id, city_id, status, request_at) VALUES
(1, 1, 10, 1, 'completed', '2023-07-12'),
(2, 2, 11, 1, 'cancelled_by_driver', '2023-07-12'),
(3, 3, 12, 6, 'completed', '2023-07-12'),
(4, 4, 13, 6, 'cancelled_by_client', '2023-07-12'),
(5, 1, 10, 1, 'completed', '2023-07-13'),
(6, 2, 11, 6, 'completed', '2023-07-13'),
(7, 3, 12, 6, 'completed', '2023-07-13'),
(8, 2, 12, 12, 'completed', '2023-07-14'),
(9, 3, 10, 12, 'completed', '2023-07-14'),
(10, 4, 13, 12, 'cancelled_by_driver', '2023-07-14');

CREATE TABLE Users (
users_id INT,
banned VARCHAR(3),
role VARCHAR(10)
);

INSERT INTO Users (users_id, banned, role) VALUES
(1, 'No', 'client'),
(2, 'Yes', 'client'),
(3, 'No', 'client'),
(4, 'No', 'client'),
(10, 'No', 'driver'),
(11, 'No', 'driver'),
(12, 'No', 'driver'),
(13, 'No', 'driver');```

Now below is how we can calculate the ride cancellation rate using SQL:

```WITH UnbannedTrips AS (
SELECT
t.request_at AS Day,
COUNT(CASE WHEN t.status LIKE 'cancelled%' THEN 1 END) AS canceled_requests,
COUNT(*) AS total_requests
FROM
Trips t
WHERE
u1.banned = 'No' AND u2.banned = 'No'
GROUP BY
t.request_at
)
SELECT
Day,
ROUND(canceled_requests / NULLIF(total_requests, 0), 2) AS `Cancellation Rate`
FROM
UnbannedTrips
ORDER BY
Day;```
```+------------+-------------------+
| Day        | Cancellation Rate |
+------------+-------------------+
| 2023-07-12 |              0.33 |
| 2023-07-13 |              0.00 |
| 2023-07-14 |              0.50 |
+------------+-------------------+
3 rows in set (0.01 sec)```

The above solution uses a Common Table Expression (CTE) named UnbannedTrips to calculate the cancellation rate for ride requests involving unbanned users. The CTE performs a join between the Trips and Users tables based on the client and driver IDs, filtering for unbanned users. It aggregates the counts of cancelled requests and total requests per day. The main query then selects the day and calculates the cancellation rate by dividing the cancelled requests by the total requests, rounded to two decimal places. The result is then ordered by the day.

### Summary

So our solution to calculate the ride cancellation rate uses Common Table Expression (CTE) to filter ride trips involving unbanned users. By joining the “Trips” and “Users” tables based on client and driver IDs, it calculates the counts of cancelled and total requests for each day. The main query then computes the cancellation rate by dividing the cancelled requests by the total requests, rounding the result to two decimal places. I hope you liked this article on how to calculate Ride Cancellation Rate using SQL. Feel free to ask valuable questions in the comments section below.

##### Aman Kharwal

I'm a writer and data scientist on a mission to educate others about the incredible power of dataðŸ“ˆ.

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