Find Customer Referee · Interview Problem

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Leetcode

Easy

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Find Customer Referee

Return customers whose referee is not a specific value, while also keeping customers with no referee.

Acceptance 100%

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Problem Statement

Problem

You are given a table of customers with at least these columns:

id: customer identifier
name: customer name
referee_id: identifier of the customer who referred them, or NULL if they were not referred

Write a query to return the names of customers who were not referred by the customer with id = 2.

A customer should be included if:

referee_id is anything other than 2, or
referee_id is NULL.

Return the result set with the customer names in any order.

Input Format

A Customer table containing customer records with columns similar to:

id
name
referee_id

Output Format

Return one column:

name

Constraints

referee_id may be NULL.
Exclude only customers whose referee_id = 2.
The ordering of the output does not matter.

Examples

Sample cases returned by the problem API.

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 |
+------+

Explanation

Exclude customers whose referee is 2. Keep rows where referee_id is NULL or any value other than 2.

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