Leetcode SQL

584. Find Customer Referee

Given a table customer holding customers information and the referee.

+------+------+-----------+
| id   | name | referee_id|
+------+------+-----------+
|    1 | Will |      NULL |
|    2 | Jane |      NULL |
|    3 | Alex |         2 |
|    4 | Bill |      NULL |
|    5 | Zack |         1 |
|    6 | Mark |         2 |
+------+------+-----------+

Write a query to return the list of customers NOT referred by the person with id ‘2’.

For the sample data above, the result is:

+------+
| name |
+------+
| Will |
| Jane |
| Bill |
| Zack |
+------+

Solution:

select name from customer
where referee_id != 2 or referee_id is null;

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