[프로그래머스] 오프라인/온라인 판매 데이터 통합하기 Lv.4

SELECT date_format(SALES_DATE, '%Y-%m-%d') as 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 date_format(SALES_DATE, '%Y-%m-%d') as SALES_DATE, PRODUCT_ID, NULL as USER_ID, SALES_AMOUNT FROM OFFLINE_SALE
WHERE SALES_DATE BETWEEN '2022-03-01' and '2022-03-31'

ORDER BY SALES_DATE, PRODUCT_ID, USER_ID