[SQL문제풀기] Binary Tree Nodes

문제

Binary Tree Nodes | HackerRank

Write a query to find the node type of BST ordered by the value of the node.

https://www.hackerrank.com/challenges/binary-search-tree-1/problem?isFullScreen=true

MySQL, Oracle, MS SQL Server, DB2

내가 작성한 정답

select n, 
       case when p is null then 'Root'
            when n in (select p.n from bst p left join bst d on p.n = d.p where d.n is null) then 'Leaf'
            else 'Inner' end tree
from bst
order by n;

내가 작성한 정답 2

select n, 
       case when p is null then 'Root'
            when n not in (select p from bst where p is not null) then 'Leaf'
            else 'Inner' end tree
from bst
order by n;