[HR] Binary Tree Nodes

• Advanced Select > Scalar subquery > case when
  

• input
  

• output
  

select t.n
      ,case when t.p is null then "Root"
            when t.n in (select t1.p from bst t1 where t1.p is not null) then "Inner"
            else "Leaf" end as "result"
from bst t
order by t.n