题目来源：小红书。

1 题目

现有一张订单表 t_order 有订单ID、用户ID、商品ID、购买商品数量、购买时间，请查询出每个用户的第一条记录和最后一条记录。样例数据如下：

+-----------+----------+-------------+-----------+------------------------+
| order_id  | user_id  | product_id  | quantity  |     purchase_time      |
+-----------+----------+-------------+-----------+------------------------+
| 1         | 1        | 1001        | 1         | 2023-03-13 08:30:00.0  |
| 2         | 1        | 1002        | 1         | 2023-03-13 10:45:00.0  |
| 3         | 1        | 1001        | 1         | 2023-03-13 10:45:01.0  |
| 4         | 2        | 1001        | 3         | 2023-03-13 14:20:00.0  |
| 5         | 3        | 1003        | 1         | 2023-03-13 16:15:00.0  |
| 6         | 3        | 1002        | 1         | 2023-03-13 12:10:00.0  |
| 7         | 3        | 1001        | 1         | 2023-03-13 12:10:01.0  |
| 8         | 4        | 1002        | 2         | 2023-03-13 09:00:00.0  |
| 9         | 4        | 1003        | 1         | 2023-03-13 11:30:00.0  |
| 10        | 4        | 1004        | 3         | 2023-03-13 13:40:00.0  |
| 11        | 4        | 1001        | 1         | 2023-03-13 17:25:00.0  |
| 12        | 4        | 1002        | 2         | 2023-03-13 15:05:00.0  |
| 13        | 4        | 1004        | 1         | 2023-03-13 11:55:00.0  |
+-----------+----------+-------------+-----------+------------------------+

2 建表语句

--建表语句
CREATE TABLE t_order (order_id INT,user_id INT,product_id INT,quantity INT,purchase_time TIMESTAMP
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
STORED AS TEXTFILE;--数据插入语句
INSERT INTO t_order VALUES
(1, 1, 1001, 1, '2023-03-13 08:30:00'),
(2, 1, 1002, 1, '2023-03-13 10:45:00'),
(3, 1, 1001, 1, '2023-03-13 10:45:01'),
(4, 2, 1001, 3, '2023-03-13 14:20:00'),
(5, 3, 1003, 1, '2023-03-13 16:15:00'),
(6, 3, 1002, 1, '2023-03-13 12:10:00'),
(7, 3, 1001, 1, '2023-03-13 12:10:01'),
(8, 4, 1002, 2, '2023-03-13 09:00:00'),
(9, 4, 1003, 1, '2023-03-13 11:30:00'),
(10, 4, 1004, 3, '2023-03-13 13:40:00'),
(11, 4, 1001, 1, '2023-03-13 17:25:00'),
(12, 4, 1002, 2, '2023-03-13 15:05:00'),
(13, 4, 1004, 1, '2023-03-13 11:55:00');

3 题解

（1）添加行号

使用row_number()根据用户进行分组，根据时间分别进行正向排序和逆向排序，增加两个行号,分别为asc_rn和desc_rn

select order_id,user_id,product_id,quantity,purchase_time,row_number() over (partition by user_id order by purchase_time asc)  as asc_rn,row_number() over (partition by user_id order by purchase_time desc) as desc_rn
from t_order;

执行结果

+-----------+----------+-------------+-----------+------------------------+---------+----------+
| order_id  | user_id  | product_id  | quantity  |     purchase_time      | asc_rn  | desc_rn  |
+-----------+----------+-------------+-----------+------------------------+---------+----------+
| 3         | 1        | 1001        | 1         | 2023-03-13 10:45:01.0  | 3       | 1        |
| 2         | 1        | 1002        | 1         | 2023-03-13 10:45:00.0  | 2       | 2        |
| 1         | 1        | 1001        | 1         | 2023-03-13 08:30:00.0  | 1       | 3        |
| 4         | 2        | 1001        | 3         | 2023-03-13 14:20:00.0  | 1       | 1        |
| 5         | 3        | 1003        | 1         | 2023-03-13 16:15:00.0  | 3       | 1        |
| 7         | 3        | 1001        | 1         | 2023-03-13 12:10:01.0  | 2       | 2        |
| 6         | 3        | 1002        | 1         | 2023-03-13 12:10:00.0  | 1       | 3        |
| 11        | 4        | 1001        | 1         | 2023-03-13 17:25:00.0  | 6       | 1        |
| 12        | 4        | 1002        | 2         | 2023-03-13 15:05:00.0  | 5       | 2        |
| 10        | 4        | 1004        | 3         | 2023-03-13 13:40:00.0  | 4       | 3        |
| 13        | 4        | 1004        | 1         | 2023-03-13 11:55:00.0  | 3       | 4        |
| 9         | 4        | 1003        | 1         | 2023-03-13 11:30:00.0  | 2       | 5        |
| 8         | 4        | 1002        | 2         | 2023-03-13 09:00:00.0  | 1       | 6        |
+-----------+----------+-------------+-----------+------------------------+---------+----------+

（2）取出第一条和最后一条记录

限制asc_rn=1取第一条，desc_rn=1 取最后一条

select order_id,user_id,product_id,quantity,purchase_time
from (select order_id,user_id,product_id,quantity,purchase_time,row_number() over (partition by user_id order by purchase_time asc)  as asc_rn,row_number() over (partition by user_id order by purchase_time desc) as desc_rnfrom t_order) t1
where t1.asc_rn = 1or t1.desc_rn = 1

执行结果

+-----------+----------+-------------+-----------+------------------------+
| order_id  | user_id  | product_id  | quantity  |     purchase_time      |
+-----------+----------+-------------+-----------+------------------------+
| 3         | 1        | 1001        | 1         | 2023-03-13 10:45:01.0  |
| 1         | 1        | 1001        | 1         | 2023-03-13 08:30:00.0  |
| 4         | 2        | 1001        | 3         | 2023-03-13 14:20:00.0  |
| 5         | 3        | 1003        | 1         | 2023-03-13 16:15:00.0  |
| 6         | 3        | 1002        | 1         | 2023-03-13 12:10:00.0  |
| 11        | 4        | 1001        | 1         | 2023-03-13 17:25:00.0  |
| 8         | 4        | 1002        | 2         | 2023-03-13 09:00:00.0  |
+-----------+----------+-------------+-----------+------------------------+