+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| year | int |
| npv | int |
+---------------+---------+
(id, year) 是该表主键.
该表有每一笔存货的年份, id 和对应净现值的信息.
表: Queries
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| year | int |
+---------------+---------+
(id, year) 是该表主键.
该表有每一次查询所对应存货的 id 和年份的信息.