1 题目描述
销售表: Sales
+-------------+-------+
| Column Name | Type |
+-------------+-------+
| sale_id | int |
| product_id | int |
| year | int |
| quantity | int |
| price | int |
+-------------+-------+
sale_id 是这个表的主键 (具有唯一值的列)
product_id 是 Product 表的外键 (reference 列)
该表的每一行显示产品 product_id 在某一年的销售情况
请注意价格是每单位的
产品表: Product
+--------------+---------+
| Column Name | Type |
+--------------+---------+
| product_id | int |
| product_name | varchar |
+--------------+---------+
product_id 是这个表的主键 (具有唯一值的列)
该表的每一行表示每种产品的产品名称
编写解决方案, 统计每个产品的销售总量
返回结果表无顺序要求
2 测试用例
输入:
Sales 表:
+---------+------------+------+----------+-------+
| sale_id | product_id | year | quantity | price |
+---------+------------+------+----------+-------+
| 1 | 100 | 2008 | 10 | 5000 |
| 2 | 100 | 2009 | 12 | 5000 |
| 7 | 200 | 2011 | 15 | 9000 |
+---------+------------+------+----------+-------+
Product 表:
+------------+--------------+
| product_id | product_name |
+------------+--------------+
| 100 | Nokia |
| 200 | Apple |
| 300 | Samsung |
+------------+--------------+
输出:
+--------------+----------------+
| product_id | total_quantity |
+--------------+----------------+
| 100 | 22 |
| 200 | 15 |
+--------------+----------------+
3 解题思路
- 对
product_id进行分组统计, 计算每种产品的quantity总数
select product_id, sum(quantity) as total_quantity
from Sales
group by product_id;
查询结果
+----------+--------------+
|product_id|total_quantity|
+----------+--------------+
|100 |22 |
|200 |15 |
+----------+--------------+
