[LeetCode] 584. Find Customer Referee

Leetcode_SQL 50

문제 출처
https://leetcode.com/studyplan/top-sql-50/

1. 문제

"Find Customer Referee" / 환자 상태

Table :Customer

Coulumn Name	Type
id	int
name	varchar
referee_id	int

input			►	output
id	name	referee_id		name
1	Will	null		Will
2	Jane	null		Jane
3	Alex	2		Bill
4	Bill	null		Zack
5	Zack	1
6	Mark	2

 

CheckPoint
1. referee_id가 2가 아닌 회원들만 조회

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2. 문제 풀이

1차시. 정답
1. referee_id = null or referee_id != 2

SELECT name
FROM Customer
WHERE referee_id != 2 or referee_id is null