https://github.com/billwallis/sql-problems
Solutions to SQL problems.
https://github.com/billwallis/sql-problems
sql
Last synced: about 2 months ago
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Solutions to SQL problems.
- Host: GitHub
- URL: https://github.com/billwallis/sql-problems
- Owner: billwallis
- Created: 2024-04-26T21:31:36.000Z (almost 2 years ago)
- Default Branch: main
- Last Pushed: 2025-10-07T06:33:14.000Z (6 months ago)
- Last Synced: 2025-10-07T08:34:39.912Z (6 months ago)
- Topics: sql
- Homepage:
- Size: 283 KB
- Stars: 9
- Watchers: 1
- Forks: 2
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Codeowners: .github/CODEOWNERS
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---
# SQL Problems
Solutions to SQL problems.
I've only bothered solving the hardest free problems, and I'll add some notes on what I thought of the platform below.
> [!WARNING]
>
> This repository will contain spoilers for the problems. If you want to solve them yourself, do not look at the solutions.
## Pre-requisites
This project uses [Docker](https://www.docker.com/) to spin up the databases:
- https://docs.docker.com/get-docker/
## Quick start
Just run Docker's `compose` command.
```bash
docker compose --profile build up --detach
docker compose down --volumes # when you're finished
```
To build all services, skip the `--profile build` flag; to customise which services to build, adjust the `docker-compose.yaml` file.
You can connect to the databases using any of your favourite SQL clients.
## Reviews
Reviews of the platforms can be found at:
- [src/reviews.md](src/reviews.md)
These are just my opinions, and you may have a different experience.
There were some sites that I loved (⭐), some that were okay (👍), and some that I didn't like at all (💩). Similarly, some sites are totally free (🆓) and others have paid features (💰). I didn't try any sites that were completely paid.
The platforms I've reviewed so far are listed below by their relative difficulty (for me).
### 🟢 Easy
- [SQL Island](https://sql-island.informatik.uni-kl.de/)👍🆓 ([review](src/reviews.md#sql-island))
- [SQL Murder Mystery](https://mystery.knightlab.com/) 👍🆓 ([review](src/reviews.md#sql-murder-mystery))
- [SQLNoir](https://www.sqlnoir.com/) ⭐🆓 ([review](src/reviews.md#sqlnoir))
- [Analyst Builder](https://www.analystbuilder.com/) ⭐💰 ([review](src/reviews.md#analyst-builder))
- [Learn SQL (SQL Practice)](https://www.sql-practice.com/) ⭐🆓 ([review](src/reviews.md#learn-sql-sql-practice))
- [SQL Premier League](https://sqlpremierleague.com/challenges/) 👍💰 ([review](src/reviews.md#sql-premier-league))
- [SQL Short Reads](https://sqlshortreads.com/sql-practice-problems/) 👍🆓 ([review](src/reviews.md#sql-short-reads))
- [StrataScratch](https://platform.stratascratch.com/coding) 👍💰 ([review](src/reviews.md#stratascratch))
- [Lost at SQL](https://lost-at-sql.therobinlord.com/) 💩🆓 ([review](src/reviews.md#lost-at-sql))
### 🟠 Medium
- [Zachary Thomas SQL Questions](https://quip.com/2gwZArKuWk7W) 💩🆓 ([review](src/reviews.md#zachary-thomas-sql-questions))
- [NamasteSQL](https://www.namastesql.com/coding-problems) 💩💰 ([review](src/reviews.md#namastesql))
- [DataLemur](https://datalemur.com/) ⭐🆓 ([review](src/reviews.md#datalemur))
- [SQL Squid Game (DataLemur Game)](https://datalemur.com/sql-game) 👍🆓 ([review](src/reviews.md#sql-squid-game-datalemur-game))
- [LeetCode](https://leetcode.com/problemset/database/) 👍💰 ([review](src/reviews.md#leetcode))
- [HackerRank](https://www.hackerrank.com/domains/sql) ⭐💰 ([review](src/reviews.md#hackerrank))
- [DataExpert.io](https://dataexpert.io/questions) 👍💰 ([review](src/reviews.md#dataexpertio))
- [Advent of SQL](https://adventofsql.com/) 👍🆓 ([review](src/reviews.md#advent-of-sql))
- [Claire Carrol's Advanced SQL Challenges](https://github.com/clrcrl/advanced-sql) ⭐🆓 ([review](src/reviews.md#claire-carrols-advanced-sql-challenges))
- [8 Week SQL Challenge (Data with Danny)](https://8weeksqlchallenge.com/) ⭐🆓 ([review](src/reviews.md#8-week-sql-challenge-data-with-danny))
### 🔴 Hard
- [Interview Query](https://www.interviewquery.com/questions?tags=SQL) ⭐💰 ([review](src/reviews.md#interview-query))
- [Noah's Rug (Hanukkah of Data)](https://hanukkah.bluebird.sh/5784/) ⭐🆓 ([review](src/reviews.md#noahs-rug-hanukkah-of-data))
- [AdvancedSQLPuzzles](https://advancedsqlpuzzles.com/) ⭐🆓 ([review](src/reviews.md#advancedsqlpuzzles))
- [Challenging SQL Problems](https://billwallis.github.io/sql-learning-materials/challenging-sql-problems/challenging-sql-problems/) 🆓 ([review](src/reviews.md#challenging-sql-problems))
### ⭕ Skipped
There were some problem sites that I chose to skip completely:
- [w3resource](https://www.w3resource.com/sql-exercises/): This has an impressive number of free questions (2,605!), but none of them are hard. Good for beginners that want an "endless" list of questions to practice on.
- [CodeChef](https://www.codechef.com/learn): No free hard questions.
- [Code360](https://www.naukri.com/code360/problem-lists/top-100-sql-problems): Email registration was broken. The "hard" and "ninja" questions all look fairly easy.
- [SQL Police Department](https://sqlpd.com/): This uses a point-and-click interface, you don't actually write the SQL yourself. Might be good for complete beginners. Has some free "cases" to solve.
- [SQL Practice](https://sqlpractice.io/practice-questions): No free hard questions (yet). Feels heavily AI-generated, so concerned about the quality of the data/questions/platform.
For clarity, I'm only reviewing problem sites and the following are (interactive) courses/tutorials, so I've also skipped these:
- [Khan Academy](https://www.khanacademy.org/search?page_search_query=sql)
- [SQLZoo](https://sqlzoo.net/wiki/SQL_Tutorial)
- [Codecademy](https://www.codecademy.com/catalog/language/sql)
- [SQLBolt](https://sqlbolt.com/)
- [Udacity](https://www.udacity.com/catalog?searchValue=sql)
- [DataCamp](https://www.datacamp.com/courses-all?q=sql)
- [Coursera](https://www.coursera.org/search?query=sql)
- [LearnSQL](https://learnsql.com/)
- [Mode](https://mode.com/sql-tutorial)
- [W3Schools](https://www.w3schools.com/sql/)