[프로그래머스 코딩테스트] oracle Lv.3 카테고리별 도서 판매량 집계하기

 

 

SELECT b.CATEGORY,	sum(s.sales) as TOTAL_SALES
from  book b, book_sales s
where b.book_id = s.book_id
and to_char(SALES_DATE,'yyyy-mm') ='2022-01'
group by b.category
order by CATEGORY