一、力扣链接
LeetCode_262
二、题目描述
表：Trips
+-------------+----------+ | Column Name | Type | +-------------+----------+ | id | int | | client_id | int | | driver_id | int | | city_id | int | | status | enum | | request_at | varchar | +-------------+----------+ id 是这张表的主键（具有唯一值的列）。 这张表中存所有出租车的行程信息。每段行程有唯一 id ，其中 client_id 和 driver_id 是 Users 表中 users_id 的外键。 status 是一个表示行程状态的枚举类型，枚举成员为(‘completed’, ‘cancelled_by_driver’, ‘cancelled_by_client’) 。
表：Users
+-------------+----------+ | Column Name | Type | +-------------+----------+ | users_id | int | | banned | enum | | role | enum | +-------------+----------+ users_id 是这张表的主键（具有唯一值的列）。 这张表中存所有用户，每个用户都有一个唯一的 users_id ，role 是一个表示用户身份的枚举类型，枚举成员为 (‘client’, ‘driver’, ‘partner’) 。 banned 是一个表示用户是否被禁止的枚举类型，枚举成员为 (‘Yes’, ‘No’) 。
取消率 的计算方式如下：(被司机或乘客取消的非禁止用户生成的订单数量) / (非禁止用户生成的订单总数)。
编写解决方案找出 "2013-10-01" 至 "2013-10-03" 期间非禁止用户（乘客和司机都必须未被禁止）的取消率。非禁止用户即 banned 为 No 的用户，禁止用户即 banned 为 Yes 的用户。其中取消率 Cancellation Rate 需要四舍五入保留 两位小数 。
返回结果表中的数据 无顺序要求 。
三、目标拆解
四、建表语句
Create table If Not Exists Trips (id int, client_id int, driver_id int, city_id int, status ENUM('completed', 'cancelled_by_driver', 'cancelled_by_client'), request_at varchar(50))
Create table If Not Exists Users (users_id int, banned varchar(50), role ENUM('client', 'driver', 'partner'))
Truncate table Trips
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('1', '1', '10', '1', 'completed', '2013-10-01')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('2', '2', '11', '1', 'cancelled_by_driver', '2013-10-01')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('3', '3', '12', '6', 'completed', '2013-10-01')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('4', '4', '13', '6', 'cancelled_by_client', '2013-10-01')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('5', '1', '10', '1', 'completed', '2013-10-02')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('6', '2', '11', '6', 'completed', '2013-10-02')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('7', '3', '12', '6', 'completed', '2013-10-02')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('8', '2', '12', '12', 'completed', '2013-10-03')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('9', '3', '10', '12', 'completed', '2013-10-03')
insert into Trips (id, client_id, driver_id, city_id, status, request_at) values ('10', '4', '13', '12', 'cancelled_by_driver', '2013-10-03')
Truncate table Users
insert into Users (users_id, banned, role) values ('1', 'No', 'client')
insert into Users (users_id, banned, role) values ('2', 'Yes', 'client')
insert into Users (users_id, banned, role) values ('3', 'No', 'client')
insert into Users (users_id, banned, role) values ('4', 'No', 'client')
insert into Users (users_id, banned, role) values ('10', 'No', 'driver')
insert into Users (users_id, banned, role) values ('11', 'No', 'driver')
insert into Users (users_id, banned, role) values ('12', 'No', 'driver')
insert into Users (users_id, banned, role) values ('13', 'No', 'driver')五、过程分析
1、过滤banned为NO的数据
2、按日期分组，计算订单数，根据结果字段命名
六、代码实现
select request_at Day,round(count(case when status in ('cancelled_by_driver', 'cancelled_by_client') then id else null end)/count(id), 2) `Cancellation Rate`
from Trips t join Users u
on t.client_id = u.users_id
where request_at between '2013-10-01' and '2013-10-03'
and client_id in (select users_id from users where banned = 'No')
and driver_id in (select users_id from users where banned = 'No')
group by request_at;七、结果验证
八、小结
1、子查询 + group by + count() + round()
2、主要是过滤出乘客和司机都未被禁止的数据