[SQL문제다시풀기] 오프라인/온라인 판매 데이터 통합하기 - union

문제

MYSQL

내가 작성한 정답

SELECT date_format(sales_date,'%Y-%m-%d') sales_date,
        product_id, user_id, sales_amount
from online_sale
where date_format(sales_date,'%y%m') = '2203'
union
select date_format(sales_date,'%Y-%m-%d') sales_date,
        product_id, null as user_id, sales_amount
from offline_sale
where date_format(sales_date,'%y%m') ='2203'
order by 1 asc, 2 asc, 3 asc

ORACLE

내가 작성한 정답

select to_char(sales_date,'yyyy-mm-dd') SALES_DATE,
        PRODUCT_ID, USER_ID, SALES_AMOUNT
from online_sale
where to_char(sales_date,'yymm') = '2203'
union
select to_char(sales_date,'yyyy-mm-dd') sales_date,
        product_id, null as user_id, sales_amount
from offline_sale
where to_char(sales_date,'yymm') = '2203'
order by sales_date asc, product_id asc, user_id asc