오프라인/온라인 판매 데이터 통합하기(Programmers)

답 쿼리입니다.

SELECT *
FROM(
    SELECT DATE_FORMAT(SALES_DATE, '%Y-%m-%d') SALES_DATE
         , PRODUCT_ID
         , USER_ID
         , SALES_AMOUNT
    FROM ONLINE_SALE

    UNION ALL

    SELECT DATE_FORMAT(SALES_DATE, '%Y-%m-%d') SALES_DATE
         , PRODUCT_ID
         , NULL AS USER_ID
         , SALES_AMOUNT
    FROM OFFLINE_SALE) AS T
WHERE SALES_DATE LIKE '2022-03%'
ORDER BY SALES_DATE, PRODUCT_ID, USER_ID