README_EN.md

584. Find Customer Referee

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Description

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.

The query 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 |
+------+

Solutions

SQL

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

MySQL can use IFNULL():

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