LeetCode：Database 62.指定日期的产品价格

Posted 2021-06-26 Xiao Miao

要求：写一段 SQL来查找在 2019-08-16 时全部产品的价格，假设所有产品在修改前的价格都是 10。

Products 表的结构：

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| product_id    | int     |
| new_price     | int     |
| change_date   | date    |
+---------------+---------+
这张表的主键是 (product_id, change_date)。
这张表的每一行分别记录了 某产品 在某个日期 更改后 的新价格。

Products 表:

+------------+-----------+-------------+
| product_id | new_price | change_date |
+------------+-----------+-------------+
| 1          | 20        | 2019-08-14  |
| 2          | 50        | 2019-08-14  |
| 1          | 30        | 2019-08-15  |
| 1          | 35        | 2019-08-16  |
| 2          | 65        | 2019-08-17  |
| 3          | 20        | 2019-08-18  |
+------------+-----------+-------------+

Result Table:

+------------+-------+
| product_id | price |
+------------+-------+
| 2          | 50    |
| 1          | 35    |
| 3          | 10    |
+------------+-------+

SQL语句：

with b as(
select product_id,new_price as price
from(
select product_id,new_price,row_number() over(partition by product_id order by change_date desc) as r
from products 
where change_date<='2019-08-16')a 
where r=1)

select * from b
union all
select distinct product_id,10 as price
from products
where product_id not in(select product_id from b);