프로그래머스 SQL 오프라인/온라인 판매 데이터 통합하기

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

WITH TEMP AS (
    SELECT *
    FROM ONLINE_SALE
    WHERE YEAR(SALES_DATE) = 2022
    AND MONTH(SALES_DATE) = 3
),  
TEMP2 AS (
    SELECT *
    FROM OFFLINE_SALE
    WHERE YEAR(SALES_DATE) = 2022
    AND MONTH(SALES_DATE) = 3
)


SELECT DATE_FORMAT(SALES_DATE, '%Y-%m-%d') AS SALES_DATE, PRODUCT_ID AS PRODUCT_ID, USER_ID AS USER_ID,  SALES_AMOUNT AS SALES_AMOUNT
FROM TEMP
UNION
SELECT SALES_DATE, PRODUCT_ID, NULL AS USER_ID, SALES_AMOUNT
FROM TEMP2
ORDER BY 1, 2, 3