[프로그래머스][SQL] 오프라인/온라인 판매 데이터 통합하기

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

프로그래머스

 

ONLINE_SALE 테이블과 OFFLINE_SALE 테이블에서 

2022년 3월의 오프라인/온라인 상품 판매 데이터의 

판매 날짜, 상품ID, 유저ID, 판매량을 출력하는 SQL문을 작성해주세요. 

OFFLINE_SALE 테이블의 판매 데이터의 USER_ID 값은 NULL 로 표시해주세요. 

결과는 판매일을 기준으로 오름차순 정렬해주시고 판매일이 같다면 상품 ID를 기준으로 오름차순, 상품ID까지 같다면 유저 ID를 기준으로 오름차순 정렬해주세요.

 

(
    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