[LeetCode] 183. Customers Who Never Order

😎풀이

1. LEFT JOIN을 통해 Orders.customerId와 Customers.id를 활용하여 테이블 병합
2. 병합된 테이블에서 Orders.customerId컬럼이 존재하지 않는 행 탐색
3. 해당 행 반환

SELECT c.name AS Customers
FROM Customers AS c
LEFT JOIN Orders AS o ON c.id = o.customerId
WHERE o.customerId IS NULL