力扣-数据库-262-行程和用户

Trips 表中存所有出租车的行程信息。每段行程有唯一键 Id，Client_Id 和 Driver_Id 是 Users 表中 Users_Id 的外键。Status 是枚举类型，枚举成员为 (‘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

Users 表存所有用户。每个用户有唯一键 Users_Id。Banned 表示这个用户是否被禁止，Role 则是一个表示（‘client’, ‘driver’, ‘partner’）的枚举类型。

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

写一段 SQL 语句查出 2013年10月1日 至 2013年10月3日 期间非禁止用户的取消率。基于上表，你的 SQL 语句应返回如下结果，取消率（Cancellation Rate）保留两位小数。
|------------|-------------------|

Day	Cancellation Rate
2013-10-01	0.33
2013-10-02	0.00
2013-10-03	0.50

-- 非禁止用户取消率=非禁止用户行程取消总数(包括司机取消的)/非禁止用户行程总数
方法一：
select Request_at day,round(nvl(sum(case when Status = 'completed' then 0 else 1 end),0)/count(1),2)  "Cancellation Rate" 
from(
select  A.status, A.request_at from Trips A
join users B on A.client_id = B.users_id
where B.banned = 'No' and A.request_at between '2013-10-01' and '2013-10-03') group by Request_at
--方法二：
select B.day,round(nvl(A.num,0)/B.num,2) "Cancellation Rate" from 
(select nvl(count(*),0) num,Request_at Day from Trips A 
join users B on A.Client_Id=B.Users_Id
--join users C on A.Client_Id=C.Users_Id
where B.Banned='No' and A.Status=any('cancelled_by_driver','cancelled_by_client')
 and A.Request_at between '2013-10-01' and '2013-10-03'
group by Request_at) A
right join  --使用外连接  防止丢失数据
(select nvl(count(*),1) num,Request_at Day from Trips A 
join users B on A.Client_Id=B.Users_Id
--join users C on A.Client_Id=C.Users_Id
where B.Banned='No'  and A.Request_at between '2013-10-01' and '2013-10-03'
group by Request_at) B on A.Day=B.Day order by B.day