Top Users by Category | Dataford Interview Questions

HackerRank Product Analytics wants to compare user activity across challenge categories. Write a PostgreSQL query that identifies the top three users by accepted submission count in the SQL and Algorithms categories during January 2025.

Requirements

Join users, submissions, and challenges using their key relationships.
Count accepted submissions for each user within each requested category.
Rank users separately within each category and return the top three per category.
Order the output by category and rank. Break ties alphabetically by username.

Representative Data

Schema

users

Column	Type	Description
user_idPK	INT	Unique HackerRank user identifier
username	VARCHAR(50)	HackerRank username
email	VARCHAR(120)	User email address

submissions

Column	Type	Description
submission_idPK	INT	Unique submission identifier
user_id	INT	User who made the submission
challenge_id	INT	Challenge associated with the submission
status	VARCHAR(20)	Submission result, such as accepted or rejected
submitted_at	TIMESTAMP	Time the submission was created

challenges

Column	Type	Description
challenge_idPK	INT	Unique challenge identifier
title	VARCHAR(100)	Challenge title
category	VARCHAR(50)	Challenge category

Your question is Top Users by Category. Start with the requirements and the three tables in the Question tab.

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Problem