GROUP BY - 저자 별 카테고리 별 매출액 집계하기 문제 링크 - https://school.programmers.co.kr/learn/courses/30/lessons/144856 내가 풀어본 오라클 정답 SELECT A.AUTHOR_ID, C.AUTHOR_NAME, A.CATEGORY, SUM(A.PRICE * B.SALES) AS TOTAL_SALES FROM BOOK A, (SELECT * FROM BOOK_SALES WHERE TO_CHAR(SALES_DATE,'YYYY-MM') IN ('2022-01')) B, AUTHOR C WHERE A.BOOK_ID =B.BOOK_ID AND A.AUTHOR_ID = C.AUTHOR_ID GROUP BY A.CATEGORY,A.AUTHOR_ID,C...
