销售表 Sales:
+-------------+-------+
| Column Name | Type |
+-------------+-------+
| sale_id | int |
| product_id | int |
| year | int |
| quantity | int |
| price | int |
+-------------+-------+
sale_id 是此表的主键。
产品 ID 是产品表的外键。
请注意,价格是按每单位计的。
产品表 Product:
+--------------+---------+
| Column Name | Type |
+--------------+---------+
| product_id | int |
| product_name | varchar |
+--------------+---------+
产品 ID 是此表的主键。
编写一个 SQL 查询,选出每个销售产品的 第一年 的 产品 id、年份、数量 和 价格。
查询结果格式如下:
Sales table:
+---------+------------+------+----------+-------+
| sale_id | product_id | year | quantity | price |
+---------+------------+------+----------+-------+
| 1 | 100 | 2008 | 10 | 5000 |
| 2 | 100 | 2009 | 12 | 5000 |
| 7 | 200 | 2011 | 15 | 9000 |
+---------+------------+------+----------+-------+
Product table:
+------------+--------------+
| product_id | product_name |
+------------+--------------+
| 100 | Nokia |
| 200 | Apple |
| 300 | Samsung |
+------------+--------------+
Result table:
+------------+------------+----------+-------+
| product_id | first_year | quantity | price |
+------------+------------+----------+-------+
| 100 | 2008 | 10 | 5000 |
| 200 | 2011 | 15 | 9000 |
+------------+------------+----------+-------+
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/product-sales-analysis-iii
著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
审题:查询每个产品销售第一年的信息。
思考:按照年份和产品id分组,找出年份最小的,有些只有一个。
解题:
解法一
找到每个商品第一次销售的年份.
应用MIN函数和group by.
-- 最小的年份
select S.product_id,min(S.year) as first_year
from Sales as S group by S.product_id;
(
select S.product_id,min(S.year) as `first_year`
from Sales as S
group by S.product_id
) as A
再连接Sales表取出first_year时的信息.
-- 练习
select A.product_id,A.first_year,B.quantity,B.price
from (
select S.product_id,min(S.year) as `first_year`
from Sales as S
group by S.product_id
) AS A join Sales as B on(A.product_id = B.product_id and A.first_year = B.year);
select A.product_id,A.first_year,B.quantity,B.price
from
(
select S.product_id,min(S.year) as `first_year`
from Sales as S
group by S.product_id
) as A
join Sales as B
on(A.product_id = B.product_id and A.first_year = B.year)
解法二
思路同解法一.
但应用IN.
select product_id,S.year as `first_year`,quantity,price
from Sales as S
where (S.product_id,S.year) in (
select product_id,min(year)
from Sales
group by product_id
)
或
select product_id,S.year as `first_year`,quantity,price
from Sales as S
where S.year in (
select min(year)
from Sales
where product_id = S.product_id
)
知识点:
IN 操作符允许您在 WHERE 子句中规定多个值。