[SQL]오프라인/온라인 판매 데이터 통합하기

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

프로그래머스

with a as (
select
    sales_date
    , product_id
    , user_id
    , sum(sales_amount) as sales_amount
from ONLINE_SALE
where year(sales_date) = 2022 and month(sales_date) = 3
group by 1, 2, 3
)
, b as (
select
    sales_date
    , product_id
    , NULL as user_id
    , sum(sales_amount) as sales_amount
from OFFLINE_SALE
where year(sales_date) = 2022 and month(sales_date) = 3
group by 1, 2, 3
)
, c as  (
select
        *
    from a
    union all
    select
    *
    from b
)
select
    DATE_FORMAT(SALES_DATE,'%Y-%m-%d') sales_date
    , product_id
    , user_id
    , sales_amount
from c
order by 1, 2, 3