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584. Find Customer Referee

EasyLeetCode
Column NameType
idint
namevarchar
referee_idint

In SQL, 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.

Find the names of the customer that are not referred by the customer with id = 2.

Return the result table in any order.

The result format is in the following example.

Example 1:

Input: Customer table:

idnamereferee_id
1Willnull
2Janenull
3Alex2
4Billnull
5Zack1
6Mark2

Output:

name
Will
Jane
Bill
Zack

How to solve the problem

SQL or Pandas

Code

Python
import pandas as pd

def find_customer_referee(customer: pd.DataFrame) -> pd.DataFrame:
    result = customer[(customer['referee_id'] != 2) | (customer['referee_id'].isnull())][['name']]
    return result
sql
SELECT name FROM Customer WHERE referee_id IS NULL OR referee_id != 2;

Complexity

Time complexity: O(1)

Space complexity: O(1)

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