PROBLEM STATEMENT:
The Trips table holds all taxi trips. Each trip has a unique Id, while Client_Id and Driver_Id are both foreign keys to the Users_Id at the Users table. Status is an ENUM type of (‘completed’, ‘cancelled_by_driver’, ‘cancelled_by_client’).
| Id | Client_Id | Driver_Id | City_Id | Status | Request_at |
|---|---|---|---|---|---|
| 1 | 1 | 10 | 1 | completed | 2013-10-01 |
| 2 | 2 | 11 | 1 | cancelled_by_driver | 2013-10-01 |
| 3 | 3 | 12 | 6 | completed | 2013-10-01 |
| 4 | 4 | 13 | 6 | cancelled_by_client | 2013-10-01 |
| 5 | 1 | 10 | 1 | completed | 2013-10-02 |
| 6 | 2 | 11 | 6 | completed | 2013-10-02 |
| 7 | 3 | 12 | 6 | completed | 2013-10-02 |
| 8 | 2 | 12 | 12 | completed | 2013-10-03 |
| 9 | 3 | 10 | 12 | completed | 2013-10-03 |
| 10 | 4 | 13 | 12 | cancelled_by_driver | 2013-10-03 |
The Users table holds all users. Each user has an unique Users_Id, and Role is an ENUM type of (‘client’, ‘driver’, ‘partner’).
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
Write a SQL query to find the cancellation rate of requests made by unbanned users between Oct 1, 2013 and Oct 3, 2013. For the above tables, your SQL query should return the following rows with the cancellation rate being rounded to two decimal places.
| Day | Cancellation Rate |
|---|---|
| 2013-10-01 | 0.33 |
| 2013-10-02 | 0.00 |
| 2013-10-03 | 0.50 |
SOLUTION:
SELECT a.request_at AS Day,
Round(SUM(a.can) / SUM(a.comp), 2) AS Cancellation_Rate
FROM (SELECT request_at,
CASE
WHEN T.status = T.status THEN 1
ELSE 0
END comp,
CASE
WHEN T.status IN( ‘cancelled_by_client’, ‘cancelled_by_driver’
) THEN
1
ELSE 0
END AS can
FROM trips T
join users U
ON T.client_id = U.users_id
WHERE U.banned = ‘No’) a
GROUP BY a.request_at
