[SQL문제풀기] Find Customer Referee

Can you solve this real interview question? Find Customer Referee - 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 either: 1. referred by any customer with id != 2. 2. not referred by any customer. 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 | +------+