262-TripsAndUsers.sql

-- 262. Trips and Users
-- Table: Trips
--
-- +-------------+----------+
-- | Column Name | Type     |
-- +-------------+----------+
-- | id          | int      |
-- | client_id   | int      |
-- | driver_id   | int      |
-- | city_id     | int      |
-- | status      | enum     |
-- | request_at  | date     |
-- +-------------+----------+
-- id is the primary key for this table.
-- The table holds all taxi trips. Each trip has a unique id, while client_id and driver_id are foreign keys to the users_id at the Users table.
-- Status is an ENUM type of ('completed', 'cancelled_by_driver', 'cancelled_by_client').
--  
--
-- Table: Users
--
-- +-------------+----------+
-- | Column Name | Type     |
-- +-------------+----------+
-- | users_id    | int      |
-- | banned      | enum     |
-- | role        | enum     |
-- +-------------+----------+
-- users_id is the primary key for this table.
-- The table holds all users. Each user has a unique users_id, and role is an ENUM type of ('client', 'driver', 'partner').
-- banned is an ENUM type of ('Yes', 'No').
--  
--
-- The cancellation rate is computed by dividing the number of canceled (by client or driver) requests with unbanned users by the total number of requests with unbanned users on that day.
--
-- Write a SQL query to find the cancellation rate of requests with unbanned users (both client and driver must not be banned) each day between "2013-10-01" and "2013-10-03". Round Cancellation Rate to two decimal points.
--
-- Return the result table in any order.
--
-- The query result format is in the following example.
--
--  
--
-- Example 1:
--
-- Input:
-- Trips table:
-- +----+-----------+-----------+---------+---------------------+------------+
-- | 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 |
-- +----+-----------+-----------+---------+---------------------+------------+
-- Users table:
-- +----------+--------+--------+
-- | 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 |
-- +----------+--------+--------+
-- Output:
-- +------------+-------------------+
-- | Day        | Cancellation Rate |
-- +------------+-------------------+
-- | 2013-10-01 | 0.33              |
-- | 2013-10-02 | 0.00              |
-- | 2013-10-03 | 0.50              |
-- +------------+-------------------+
-- Explanation:
-- On 2013-10-01:
--   - There were 4 requests in total, 2 of which were canceled.
--   - However, the request with Id=2 was made by a banned client (User_Id=2), so it is ignored in the calculation.
--   - Hence there are 3 unbanned requests in total, 1 of which was canceled.
--   - The Cancellation Rate is (1 / 3) = 0.33
-- On 2013-10-02:
--   - There were 3 requests in total, 0 of which were canceled.
--   - The request with Id=6 was made by a banned client, so it is ignored.
--   - Hence there are 2 unbanned requests in total, 0 of which were canceled.
--   - The Cancellation Rate is (0 / 2) = 0.00
-- On 2013-10-03:
--   - There were 3 requests in total, 1 of which was canceled.
--   - The request with Id=8 was made by a banned client, so it is ignored.
--   - Hence there are 2 unbanned request in total, 1 of which were canceled.
--   - The Cancellation Rate is (1 / 2) = 0.50
--
-- Write your MySQL query statement below
SELECT
    a.request_at AS Day,
    IFNULL(ROUND(b.num / a.num,2),0.00) AS `Cancellation Rate`
FROM
    (-- 先取出 每天的所有行程数
        SELECT
            COUNT(*) AS num,
            t.request_at
        FROM Trips AS t
        LEFT JOIN Users AS c ON c.users_id = t.client_id
        LEFT JOIN Users AS d ON d.users_id = t.driver_id
        WHERE
            c.banned = 'No' AND d.banned = 'No' -- 乘客和司机都必须未被禁止
        GROUP BY
            t.request_at
    ) AS a
LEFT JOIN
    (-- 先取出 每天的取消的行程数
        SELECT
            COUNT(*) AS num,
            t.request_at
        FROM Trips AS t
        LEFT JOIN  Users AS c ON c.users_id = t.client_id
        LEFT JOIN  Users AS d ON d.users_id = t.driver_id
        WHERE
            c.banned = 'No' AND d.banned = 'No' AND -- 乘客和司机都必须未被禁止
            t.status IN ('cancelled_by_driver','cancelled_by_client')
        GROUP BY
            t.request_at
    ) AS b
ON
    a.request_at = b.request_at
WHERE
    a.request_at BETWEEN '2013-10-01' AND '2013-10-03'