Binary tree nodes sql advanced select hackerrank solution

hackerrank binary tree nodes: a deep dive with sql solution

the "binary tree nodes" challenge on hackerrank is a classic problem designed to test your understanding of tree structures and your ability to manipulate data using sql. it requires you to classify nodes in a binary tree based on their position (root, leaf, or inner node) using information stored in a database table.

let's break down the problem, explore the concepts, and then dive into a detailed sql solution.

**problem statement:**

you are given a table `bst` representing a binary search tree. this table has two columns:

* `n`: the value of the node. this is an integer representing the data stored at each node.
* `p`: the value of the parent node. if a node is the root, `p` is `null`.

your task is to write a query that outputs the following for each node `n`:

* the value of the node `n`.
* the type of the node (root, leaf, inner).

**understanding the concepts:**

before writing the sql query, it's essential to understand the definitions of each node type within the context of the `bst` table:

* **root:** the root node is the topmost node in the tree. in the `bst` table, the root node is the only node where the `p` (parent) column is `null`.

* **leaf:** a leaf node is a node with no children. in the `bst` table, a leaf node is any node `n` that does *not* appear in the `p` column. this means no other node lists this node as its parent.

* **inner:** an inner node (also called an internal node) is a node that is neither the root nor a leaf. in the `bst` table, an inner node `n` is one that:
* has a non-null `p` value (not the root) *and*
* appears in the `p` column (has children).

**sql solution breakdown (mysql/mariadb compatible):**

here's a comprehensive sql query that addresses the problem, along with a detailed explanation:

**explanation:**

1. **`select n, case ... end`**: we're selecting two columns: the node value (`n`) and a calculated column that de ...

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