LeetCode刷题-数据库（MySQL）-1083. Sales Analysis III

1083. Sales Analysis III

一、题目描述

Table: Product

Column Name	Type
product_id	int
product_name	varchar
unit_price	int

product_id is the primary key of this table.

Table: Sales

Column Name	Type
seller_id	int
product_id	int
buyer_id	int
sale_date	date
quantity	int
price	int

This table has no primary key, it can have repeated rows.
product_id is a foreign key to Product table.

Write an SQL query that reports the products that were only sold in spring 2019. That is, between 2019-01-01 and 2019-03-31 inclusive.

The query result format is in the following example:

Product table:

product_id	product_name	unit_price
1	S8	1000
2	G4	800
3	iPhone	1400

Sales table:

seller_id	product_id	buyer_id	sale_date	quantity	price
1	1	1	2019-01-21	2	2000
1	2	2	2019-02-17	1	800
2	2	3	2019-06-02	1	800
3	3	4	2019-05-13	2	2800

Result table:

product_id	product_name
1	S8

The product with id 1 was only sold in spring 2019 while the other two were sold after.

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/sales-analysis-iii
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二、思路分析

Write an SQL query that reports the products that were only sold in spring 2019. That is, between 2019-01-01 and 2019-03-31 inclusive.
本题要求找出所有只在2019年1月1日-2019年3月31日被售出的产品。需要注意的有以下几点：

1. 题意中最重要的一点就是“只在2019年1月1日-2019年3月31日被售出”。也就是，该产品所有的销售记录都在此时间段，此外的时间段无销售记录。
2. 要实现这个目的，对product_id进行GROUP BY，只要要求每个分组中最大的销售时间小于等于"2019-03-31"，最小的销售时间大于等于"2019-01-01"即可。
3. 为了在最后显示出产品的名称，还需要对两表进行内连接JOIN。
4. 为防止出现重复记录，使用DISTINCT去重。

三、代码实现

SELECT DISTINCT
    s.product_id, p.product_name
FROM
    Sales s
JOIN
    Product p
ON
    s.product_id = p.product_id
GROUP BY
    s.product_id
HAVING
    MAX(sale_date) <= '2019-03-31'
    AND MIN(sale_date) >= '2019-01-01';