[LeetCode] Database | 183. Customers Who Never Order

Problem

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Example

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Thinking

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우선 LEFT JOIN으로 Customers에 대응하는 Order정보를 모두 가져온다.

Order 정보가 없을 경우에는 Null로 표시가 되니,

LEFT JOIN한 테이블에서 where 절로 Order 테이블의 id나 customerId가 null인 조건을 추가해주자

 

Solve

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제출 답안

 

select c.name as Customers from Customers as c
    LEFT JOIN Orders as o
    on c.id = o.customerId
    where o.customerId is null
    # where o.id is null 도 가능

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https://leetcode.com/problems/customers-who-never-order/submissions/

Customers Who Never Order - LeetCode