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leetcode/problem/find-customer-referee.html

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+<p>Table: <code>Customer</code></p>
+
+<pre>
++-------------+---------+
+| 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.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write an SQL query to report the IDs of the customer that are <strong>not referred by</strong> the customer with <code>id = 2</code>.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The query result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> 
+Customer table:
++----+------+------------+
+| id | name | referee_id |
++----+------+------------+
+| 1  | Will | null       |
+| 2  | Jane | null       |
+| 3  | Alex | 2          |
+| 4  | Bill | null       |
+| 5  | Zack | 1          |
+| 6  | Mark | 2          |
++----+------+------------+
+<strong>Output:</strong> 
++------+
+| name |
++------+
+| Will |
+| Jane |
+| Bill |
+| Zack |
++------+
+</pre>