[LeetCode][MySQL] 584. Find Customer Referee

Easy 🔗584. Find Customer Referee

📝문제 요약

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.

Example 1:

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
  • 이름 name
• FROM Customer
• WHERE
  • referee_id가 2가 아닌 것이므로 referee_id != 2
  • NULL값이 포함이 안되서 referee_id IS NULL 를 추가
  • 두 개 중 하나만 해당 되어도 출력될 수 있도록 OR을 사용

💯제출 코드

SELECT name
FROM Customer
WHERE referee_id != 2 OR referee_id IS NULL