[프로그래머스] 카테고리 별 도서 판매량 집계하기 - MySQL

https://school.programmers.co.kr/learn/courses/30/lessons/144855

프로그래머스

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SELECT b.category,sum(s.sales) as toal_sales
from book as b 
# 2022년 1월의 카테고리 별 도서 판매량을 합산하고, 
join (select book_id,sum(sales) as sales
      from book_sales
      where year(sales_date) = 2022 and month(sales_date) = 1
      group by book_id) as s
on b.book_id = s.book_id
group by category
order by category;

b 테이블(좌) / s 테이블(우)