Leetcode(Easy) - Find Customer Referee

SQL Schema

Create table If Not Exists Customer (id int, name varchar(25), referee_id int)
Truncate table Customer
insert into Customer (id, name, referee_id) values ('1', 'Will', 'None')
insert into Customer (id, name, referee_id) values ('2', 'Jane', 'None')
insert into Customer (id, name, referee_id) values ('3', 'Alex', '2')
insert into Customer (id, name, referee_id) values ('4', 'Bill', 'None')
insert into Customer (id, name, referee_id) values ('5', 'Zack', '1')
insert into Customer (id, name, referee_id) values ('6', 'Mark', '2')

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.

Question

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 |
+------+

Solution

select name
from Customer
where id not in (
    select id
    from Customer
    where referee_id = 2
)