Tree Node | Advanced SQL Interview Questions | Data Engineer Interview Questions | FAANG Interview

Video 351: This is the 32nd video of the SQL Interview Question series.

00:00 - Introduction to dataset and Question
03:10 - Approach 1: Using CTE to Identify Inner Nodes
07:30 - Approach 2: Simplified CTE Table
09:15 - Approach 3: Using a Subquery Table
10:55 - Conclusion

We are given Tree dataset where id is the unique identifier. The given structure is always a valid tree.

Each row of this table contains information about the id of a node and the id of its parent node in a tree.

Each node in the tree can be one of the three types

1. "Root" : if the node is the root of the tree which has no Parent Node.
2. "Leaf" : if the node don't have a Downstream Node
3. "Inner": If the node is neither a leaf node nor a root node, means it has a Parent Node and also a Downstream Node

In this video, I explain how to classify each node in a tree as "Root," "Inner," or "Leaf" using SQL. I cover three different approaches to solve this problem:

*** Approach 1. Using CTE to Identify Inner Nodes ***
In this approach, I utilize a Common Table Expression (CTE) to identify inner nodes and then classify nodes accordingly.

*** Approach 2. Simplified CTE Table ***
A more streamlined version of the CTE approach, focusing on identifying inner nodes with a simpler query structure.

*** Approach 3. Using a Subquery Table ***
This method uses a subquery to classify nodes without the need for CTEs, providing a different angle to solve the problem.

For a comprehensive understanding of these SQL methodologies and their application, please refer to this explanatory video.

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