[데이터분석] 코드카타 101

101. Product Sales Analysis III

https://leetcode.com/problems/product-sales-analysis-iii/description/

 

Write a solution to select the product id, year, quantity, and price for the first year of every product sold.

Return the resulting table in any order.

 

(오답)  첫 해에 판매해서 min 썼고, left join 했는데 왜 안 될까.

select b.product_id,

          min(year) first_year,

          quantity,

          price

from Sales a left join product b on a.product_id = b.product_id

group by 1

 

 

(정답) 이렇게 따로 where절로 빼서 product_id,와 year을 지정해주는 거랑 그냥 원래 select 문에서 지정하는거랑 뭐가다른거지

select product_id,

          year first_year,

          quantity,

          price

from Sales

where (product_id, year) in (select product_id,

                                   min(year) year

                                   from Sales

                                   group by 1)