leetcode

0 SELECT id, (

1 CASE

2 WHEN T.p_id IS NULL THEN 'Root'

3 WHEN P.p_id IS NOT NULL THEN 'Inner'

4 ELSE 'Leaf'

5 END

6 ) AS type

7 FROM TREE T

8 LEFT JOIN (

9 SELECT p_id, COUNT(*) AS count

10 FROM Tree

11 GROUP BY p_id

12 ) AS P

13 ON T.id = P.p_id