584-FindCustomerReferee.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 IDs 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 |
-- +------+

-- 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')

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