[SQL] 리트코드 584. Find Customer Referee

문제

Table: Customer

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| name        | varchar |
| referee_id  | int     |
+-------------+---------+

In SQL, id is the primary key column for this table.
Each row of this table indicates the id of a customer, their name, and the id of the customer who referred them.
 
Find the names of the customer that are not referred by the customer with id = 2.
Return the result table in any order.
The result format is in the following example.

 

https://leetcode.com/problems/find-customer-referee/description/

LeetCode - The World's Leading Online Programming Learning Platform

예시

Input: 
Customer table:

+----+------+------------+
| id | name | referee_id |
+----+------+------------+
| 1  | Will | null       |
| 2  | Jane | null       |
| 3  | Alex | 2          |
| 4  | Bill | null       |
| 5  | Zack | 1          |
| 6  | Mark | 2          |
+----+------+------------+

Output: 

+------+
| name |
+------+
| Will |
| Jane |
| Bill |
| Zack |
+------+

문제 풀이

SELECT name
FROM customer
WHERE IFNULL(referee_id, 0) != 2;

---

SQL을 독학하시는 분들에게 도움이 되길 바라며,

혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.