[프로그래머스] GROUP BY: 년, 월, 성별 별 상품 구매 회원 수 구하기*

https://school.programmers.co.kr/learn/courses/30/lessons/131532

프로그래머스

 

제출 코드

SELECT
    YEAR(O.SALES_DATE) AS YEAR,
    MONTH(O.SALES_DATE) AS MONTH,
    U.GENDER,
    COUNT(DISTINCT O.USER_ID) AS USERS
FROM 
    USER_INFO AS U 
 JOIN ONLINE_SALE AS O ON U.USER_ID = O.USER_ID
WHERE U.GENDER IS NOT NULL
GROUP BY 1, 2, 3
ORDER BY 1, 2, 3

 

DISTINCT : 중복 제거