SQL 584 Find Customer Referee

Table: Customer

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

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.

Write an SQL query to report the names of the customer that are not referred by the customer with id = 2.

Return the result table in any order.

Solution

注意 /(NULL/) 的情况：使用 /(is/ NULL/) 来判断

# Write your MySQL query statement below
# Write your MySQL query statement below
SELECT 
    name
FROM 
    Customer
WHERE
    referee_id != 2 OR referee_id is NULL;