---
title: "Solving the most complex SQL Problem on LeetCode | SQL Interview Question and Answer"
url: https://daily.dev/posts/solving-the-most-complex-sql-problem-on-leetcode-sql-interview-question-and-answer-ppr6mt8pv
source_url: https://www.youtube.com/watch?v=n0YG6arGHr0
type: video:youtube
source: "techTFQ"
published: 2026-05-31T07:43:14.287Z
updated: 2026-05-31T07:56:20.821Z
tags: ["sql", "postgresql"]
reading_time: 22
upvotes: 0
comments: 0
language: en
---

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# Solving the most complex SQL Problem on LeetCode | SQL Interview Question and Answer

**[techTFQ](https://daily.dev/sources/techtfq)** · 22 min read · 0 upvotes · 0 comments

## Summary

A walkthrough of LeetCode problem #1917 (Find Users With Valid E-Mails / Friends Recommendation), one of the hardest SQL problems with only 27% acceptance rate. The solution is built step-by-step in PostgreSQL/pgAdmin using CTEs, self-joins, GROUP BY with HAVING, and UNION to find pairs of users who listened to 3+ common songs on the same day and are not already friends, then returning bidirectional recommendations.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.youtube.com/watch?v=n0YG6arGHr0>

---

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

[View this post on daily.dev](https://daily.dev/posts/solving-the-most-complex-sql-problem-on-leetcode-sql-interview-question-and-answer-ppr6mt8pv)