LeetCode SQL 50 - 584. Find Customer Fefereehttps://leetcode.com/problems/find-customer-referee/description/?envType=study-plan-v2&envId=top-sql-50 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: ..