Leetcode_SQL 50 문제 출처 https://leetcode.com/studyplan/top-sql-50/ 1. 문제 "Find Customer Referee" / 환자 상태 Table :Customer Coulumn Name Type id int name varchar referee_id int input ► output id name referee_id name 1 Will null Will 2 Jane null Jane 3 Alex 2 Bill 4 Bill null Zack 5 Zack 1 6 Mark 2 CheckPoint 1. referee_id가 2가 아닌 회원들만 조회 2. 문제 풀이 1차시. 정답 1. referee_id = null or referee_id != 2 SELECT ..
