# leetcode\_584

SQL架构 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 | +------+

## Solutions

1.

```sql
# Write your MySQL query statement below
SELECT name
    FROM customer
    WHERE IFNULL(referee_id, 0) != 2
```

or

```sql
# Write your MySQL query statement below
SELECT name
    FROM customer
    WHERE referee_id IS NULL OR referee_id != 2
```

```sql
# Write your MySQL query statement below
SELECT name
    FROM customer
    WHERE id NOT IN (SELECT id FROM customer WHERE referee_id = 2)
```