[프로그래머스] 오프라인/온라인 판매 데이터 통합하기

https://school.programmers.co.kr/learn/courses/30/lessons/131537

프로그래머스

(
    SELECT
        DATE_FORMAT(SALES_DATE, '%Y-%m-%d') AS SALES_DATE,
        PRODUCT_ID,
        USER_ID,
        SALES_AMOUNT
    FROM ONLINE_SALE
    WHERE SALES_DATE LIKE '2022-03-%'
UNION
    SELECT
        DATE_FORMAT(SALES_DATE, '%Y-%m-%d') AS SALES_DATE,
        PRODUCT_ID,
        NULL AS USER_ID,
        SALES_AMOUNT
    FROM OFFLINE_SALE
    WHERE SALES_DATE LIKE '2022-03-%'
)
ORDER BY SALES_DATE, PRODUCT_ID, USER_ID

 

알아야 할 점

- NULL AS 컬럼명

- UNION