[프로그래머스] 오프라인/온라인 판매 데이터 통합하기

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

SELECT, UNION 문제
ALIAS, NULL AS 주의하기.

생각보다 오래 걸린 이유 : ORDER BY 조건 제대로 안 봄

 

-- 나의 풀이
(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')

UNION

(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')

ORDER BY SALES_DATE ASC, PRODUCT_ID ASC, USER_ID ASC