[SQL문제풀기 - Advent of SQL 2025 🎅] 신규 유입을 견인하는 카테고리

문제

solvesql.com

https://solvesql.com/problems/first-order-category/

내가 작성한 정답

MySQL, PostgreSQL, SQLite

select category, sub_category, count(distinct order_id) cnt_orders
from records
where (customer_id, order_date)  in (select customer_id, first_order_date from customer_stats)
group by category, sub_category
order by 3 desc;