[SQL智慧航行者] - 行程和用户

话不多说, 先看数据表信息.

数据表信息:

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      |  2013-10-1   |
|  2 |     2     |    11     |    1    | cancelled_by_driver|  2013-10-1   |
|  3 |     3     |    12     |    6    |     completed      |  2013-10-1   |
|  4 |     4     |    13     |    6    | cancelled_by_client|  2013-10-1   |
|  5 |     1     |    10     |    1    |     completed      |  2013-10-2   |
|  6 |     2     |    11     |    6    |     completed      |  2013-10-2   |
|  7 |     3     |    12     |    6    |     completed      |  2013-10-2   |
|  8 |     2     |    12     |    12   |     completed      |  2013-10-3   |
|  9 |     3     |    10     |    12   |     completed      |  2013-10-3   |
| 10 |     4     |    13     |    12   | cancelled_by_driver|  2013-10-3   |

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 |
+----------+--------+--------+

话不多说, 再看需求~

需求:

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。

话不多说, 进行拆解~

拆解:

select 
    t.request_at as `date`,
    round(count(case when t.status like 'cancelled%' then 1 end) / count(*), 2) as `cancellation rate`
from
    trips t
join
    users u on t.client_id = u.users_id
where
    u.banned = 'no'
    and t.request_at between '2013-10-01' and '2013-10-03'
group by
    t.request_at;

结果如下:

最后给大家介绍一下我这边的创建数据表和插入数据的操作步骤, 想要自己测试的话, 可以参考:

-- 创建 users 表
CREATE TABLE users (
    users_id INT PRIMARY KEY,
    banned VARCHAR(3),
    role VARCHAR(10)
);

-- 插入 users 数据
INSERT INTO users (users_id, banned, role)
VALUES
    (1, 'no', 'client'),
    (2, 'yes', 'client'),
    (3, 'no', 'client'),
    (4, 'no', 'client'),
    (10, 'no', 'driver'),
    (11, 'no', 'driver'),
    (12, 'no', 'driver'),
    (13, 'no', 'driver');

-- 创建 trips 表
CREATE TABLE trips (
    id INT PRIMARY KEY,
    client_id INT,
    driver_id INT,
    city_id INT,
    status VARCHAR(20),
    request_at DATE,
    FOREIGN KEY (client_id) REFERENCES users(users_id),
    FOREIGN KEY (driver_id) REFERENCES users(users_id)
);

-- 插入 trips 数据
INSERT INTO trips (id, client_id, driver_id, city_id, status, request_at)
VALUES
    (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');