Yes. Every exercise, hint, and interview set is free to start. There is no payment step.

Do I need to install a database?

No. Each query runs in SQLite inside your browser. The application database only stores accounts and saved progress.

Can I practice SQL without an account?

Yes. You can open an exercise, run SQL, and check the answer immediately. Progress stays in this browser until you create an account.

What SQL topics are covered?

SELECT, WHERE, ORDER BY, LIMIT, DISTINCT, NULL handling, JOINs, GROUP BY, HAVING, subqueries, CTEs, window functions, dates, CASE, and data cleaning.

Is QueryLab good for SQL interview preparation?

It is built for that practice. You can work through interview-style questions or start a timed set. It does not promise a job or a score on a particular company's test.

Which databases are supported?

The sandbox is SQLite. SELECT, JOIN, GROUP BY, and window functions match the SQL you will write for MySQL and PostgreSQL. Date and string functions differ, and the MySQL and PostgreSQL pages call those differences out.

SQL practice in the browser

Learn SQL by solving real-world challenges.

Practice SQL in your browser with instant feedback, realistic datasets, hints, and step-by-step explanations.

QueryLab is for students, analysts, and anyone preparing for a SQL interview. You can run queries and check answers without creating an account.

Start practicing free Explore exercises

Products still on the shelfBeginner · 8 min

List every product Northwind can still sell, with price and remaining stock.

Starter query

-- Return columns: id, name, category, price_cents, stock
SELECT

FROM products

Expected result · 7 rows

First rows of the expected result for Products still on the shelf
id	name	category	price_cents	stock
8	Ceramic Mug	Home	1800	50
2	Desk Lamp	Home	4250	40

How it works

Step 1
Choose a challenge
Pick a topic and a business question. Each one names the tables and the result you need.
Step 2
Write SQL in the browser
Use the editor with syntax highlighting. Your query runs on a sample database that resets every time.
Step 3
Get instant feedback and learn
See a clear error, or compare columns, row counts, and values. Hints stay optional.

Featured exercise categories

SQL basics

Choose columns, filter rows, and sort a result you can check.

SQL JOINs

Connect customers, orders, employees, and shipments.

GROUP BY and aggregation

Turn line items into revenue, headcount, and totals.

Subqueries

Compare a row with a number computed somewhere else.

Window functions

Rank, running totals, and retention without collapsing rows.

SQL interview questions

Practice the patterns that show up in analyst interviews.

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One-table questions on WHERE, ORDER BY, LIMIT, and NULL.

Real-world data challenges

Commerce, HR, SaaS, finance, and healthcare questions.

Why QueryLab

No installation

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QueryLab compares column names, row counts, and values after each check.

Realistic datasets

Questions come from commerce, HR, SaaS, logistics, marketing, finance, and healthcare tables.

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Open one hint at a time. The explanation appears after a correct result, and the full solution stays hidden until you ask.

Progress tracking

Completed exercises stay on this device. Create an account when you want them on another browser.

Interview preparation

Timed sets and a five-question mock sit next to the open practice catalog.

Sample challenge

List every product Northwind can still sell, with price and remaining stock.

Business question

Products still on the shelf

Merchandising is building a restock board. Out-of-stock items and products that have not been received yet should stay off the list.

products

id INTEGER · primary key
name TEXT
category TEXT
price_cents INTEGER
stock INTEGER · nullable