---
title: "Split Hierarchy - SQL Interview Query 12 | SQL Problem Level \"HARD\""
url: https://daily.dev/posts/split-hierarchy---sql-interview-query-12-sql-problem-level-hard--14yydcivp
source_url: https://www.youtube.com/watch?v=KrUIQAcFptY
type: video:youtube
source: "techTFQ"
published: 2026-05-31T07:43:11.943Z
updated: 2026-05-31T07:55:44.914Z
tags: ["sql", "postgresql"]
reading_time: 21
upvotes: 0
comments: 0
language: en
---

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# Split Hierarchy - SQL Interview Query 12 | SQL Problem Level "HARD"

**[techTFQ](https://daily.dev/sources/techtfq)** · 21 min read · 0 upvotes · 0 comments

## Summary

A walkthrough of a hard-level SQL interview problem involving splitting an employee hierarchy into teams using PostgreSQL. The solution uses a self-join to identify root-level direct reports as team anchors, then a recursive CTE to traverse the full hierarchy and assign each employee to their correct team. Key techniques include cross joins, left joins, COALESCE, ROW_NUMBER window functions, and STRING_AGG for final output formatting.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.youtube.com/watch?v=KrUIQAcFptY>

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Tags: [#sql](https://daily.dev/tags/sql), [#postgresql](https://daily.dev/tags/postgresql)

[View this post on daily.dev](https://daily.dev/posts/split-hierarchy---sql-interview-query-12-sql-problem-level-hard--14yydcivp)