오프라인/온라인 판매 데이터 통합하기

문제

코드

SELECT DATE_FORMAT(SALES_DATE,'%Y-%m-%d'), PRODUCT_ID, USER_ID, SALES_AMOUNT
FROM (
    SELECT SALES_DATE, PRODUCT_ID, USER_ID, SALES_AMOUNT
    FROM ONLINE_SALE
    WHERE SALES_DATE BETWEEN '2022-03-01' AND '2022-03-31'
    
    UNION ALL
    
    SELECT SALES_DATE, PRODUCT_ID, NULL AS USER_ID, SALES_AMOUNT
    FROM OFFLINE_SALE
    WHERE SALES_DATE BETWEEN '2022-03-01' AND '2022-03-31'
) AS COMBINED_SALES
ORDER BY SALES_DATE, PRODUCT_ID, USER_ID;

 

출처: 프로그래머스 코딩 테스트 연습, https://school.programmers.co.kr/learn/courses/30/lessons/131537