Supercloud Customer

Supercloud Customer

문제

1. 모든 product_category에서 최소 한 개의 제품을 구매한 고객

select customer_id
from (
  select cc.customer_id, count(product_category) as cnt
  from customer_contracts cc
  left join products p on cc.product_id = p.product_id
  group by cc.customer_id, p.product_category
) sub1
group by customer_id
having count(*) = (select count(distinct product_category) from products)

풀이

1️⃣ sub1: customer_contracts, products left join

2️⃣ sub1: customer_id, product_category별로 숫자세기

3️⃣ group by: customer_id 그룹

4️⃣ having: products 테이블에서 고유한 product_category 수 가져오기

5️⃣ 해당 product_category가 다 있는 customer_id 출력