Given a table customer holding customers information and the referee.
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| +------+------+-----------+
| 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:
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| +------+
| name |
+------+
| Will |
| Jane |
| Bill |
| Zack |
+------+
|
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SELECT c.name
FROM Customer c
Where c.referee_id <>2
OR c.referee_id is NULL
|