[GROUP BY, JOIN, DATE] 카테고리 별 도서 판매량 집계하기

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

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SELECT CATEGORY, SUM(SALES) AS TOTAL_SALES
FROM BOOK_SALES AS A
LEFT JOIN BOOK AS B ON A.BOOK_ID = B.BOOK_ID
WHERE DATE_FORMAT(A.SALES_DATE ,"%Y-%m")="2022-01"
GROUP BY CATEGORY
ORDER BY CATEGORY ASC