오프라인/온라인 판매 데이터 통합하기

• 문제
  
• 정답

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

SELECT DATE_FORMAT(SALES_DATE, '%Y-%m-%d') AS SALES_DATE, PRODUCT_ID, NULL, SALES_AMOUNT
FROM OFFLINE_SALE 
WHERE SALES_DATE BETWEEN '2022-03-01' AND '2022-03-31'

ORDER BY 1, 2, 3

• 결과