데이터 공부를 기록하는 공간

https://www.hackerrank.com/domains/sql?filters%5Bskills%5D%5B%5D=SQL%20%28Intermediate%29 Solve SQL Code Challenges A special-purpose language designed for managing data held in a relational database. www.hackerrank.com intermediate ☆Binary Tree Nodes select N, case when P is null then "Root" when N not in (select distinct P from BST where P is not null) then "Leaf" else "Inner" end from BST ord..