_262.sql

--262. Trips and Users
--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 clients 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        |
--+------------+-------------------+
--Credits:
--Special thanks to @cak1erlizhou for contributing this question, writing the problem description and adding part of the test cases.

select t.Request_at as Day,
round(sum(case when t.Status like 'cancelled_%' then 1 else 0 end)/count(*), 2) as 'Cancellation Rate'
from Trips t
inner join Users u
on t.Client_Id = u.Users_Id and u.Banned = 'No'
where t.Request_at between '2013-10-01' and '2013-10-03' group by t.Request_at