add 004. Binary Tree Nodes

Author: marinskiy

README.md

@@ -1,7 +1,7 @@
 <p align="center"><a href="https://www.hackerrank.com/marinskiy"><img src="https://i0.wp.com/gradsingames.com/wp-content/uploads/2016/05/856771_668224053197841_1943699009_o.png" ></a></p>
 
 # Solutions to Hackerrank practice problems
-This repository contains 65 solutions to Hackerrank practice problems with Python and Oracle SQL.
+This repository contains 66 solutions to Hackerrank practice problems with Python and Oracle SQL.
 
 Updated daily :) If it was helpful please press a star.
 
@@ -65,6 +65,7 @@ Updated daily :) If it was helpful please press a star.
     02. Advanced Select
         - Type of Triangle | [Problem](https://www.hackerrank.com/challenges/what-type-of-triangle/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/02.%20Advanced%20Select/001.%20Type%20of%20Triangle.sql) | Score: 20
         - The PADS | [Problem](https://www.hackerrank.com/challenges/the-pads/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/02.%20Advanced%20Select/002.%20The%20PADS.sql) | Score: 30
+        - Binary Tree Nodes | [Problem](https://www.hackerrank.com/challenges/binary-search-tree-1/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/02.%20Advanced%20Select/004.%20Binary%20Tree%20Nodes.sql) | Score: 30
     03. Aggregation
         - Revising Aggregations - The Count Function | [Problem](https://www.hackerrank.com/challenges/revising-aggregations-the-count-function/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/03.%20Aggregation/001.%20Revising%20Aggregations%20-%20The%20Count%20Function.sql) | Score: 10
         - Revising Aggregations - The Sum Function | [Problem](https://www.hackerrank.com/challenges/revising-aggregations-sum/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/03.%20Aggregation/002.%20Revising%20Aggregations%20-%20The%20Sum%20Function.sql) | Score: 10
@@ -88,5 +89,3 @@ Updated daily :) If it was helpful please press a star.
         - African Cities | [Problem](https://www.hackerrank.com/challenges/african-cities/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/04.%20Basic%20Join/002.%20African%20Cities.sql) | Score: 10
         - Average Population of Each Continent | [Problem](https://www.hackerrank.com/challenges/average-population-of-each-continent/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/04.%20Basic%20Join/003.%20Average%20Population%20of%20Each%20Continent.sql) | Score: 10
         - The Report | [Problem](https://www.hackerrank.com/challenges/the-report/problem) | [Solution](https://github.com/marinskiy/HackerrankPractice/blob/master/SQL/04.%20Basic%20Join/004.%20The%20Report.sql) | Score: 20
-    05. Advanced Join
-    06. Alternative Queries

SQL/02. Advanced Select/004. Binary Tree Nodes.sql

@@ -0,0 +1,12 @@
+-- # Problem: https://www.hackerrank.com/challenges/binary-search-tree-1/problem
+-- # Score: 30
+
+
+SELECT N,
+    CASE
+        WHEN P IS NULL THEN 'Root'
+        WHEN N IN (SELECT P FROM BST) THEN 'Inner'
+        ELSE 'Leaf'
+    END
+FROM BST
+ORDER BY N;