Learn SQL by running real queries

Learn SQL the way it should be taught — interactively.

SQLSimplified teaches you SQL from your first SELECT to advanced window functions with a real database running directly in your browser. No signup, no setup.

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-- Find top 5 highest-paid employees

SELECT name, salary

FROM employees

ORDER BY salary DESC

LIMIT 5;

Ran in 4ms · 5 rows returned

Your learning roadmap

Step 1

Beginner

SELECT, WHERE, ORDER BY, and the fundamentals every SQL developer starts with.

Step 2

Intermediate

GROUP BY, JOINs, subqueries, and aggregate functions for real-world queries.

Step 3

Advanced

CTEs, window functions, indexes, and query optimization for production systems.

Popular lessons

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beginner4 min

Introduction to SQL

What SQL is, why it matters, and how you'll learn it in this course.

beginner4 min

The SELECT Statement

How to choose exactly which columns you want back from a table using SELECT.

beginner5 min

Filtering Rows with WHERE

Use the WHERE clause and comparison operators to filter which rows a query returns.

Popular functions

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ABS()

numeric

Returns the absolute (non-negative) value of a number.

ARRAY_AGG()

aggregate

Collects values from a group into a single array (list).

AVG()

aggregate

Calculates the average (mean) of the values in a numeric column across a group of rows.

Practice problems

Latest examples

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Aggregate Functions: AVG, MAX, MIN, and COUNT Together

aggregate

Summarize student grades per course using AVG, MAX, MIN, and COUNT alongside a join for readable course names.

CASE Expressions: Conditional Logic in SQL

case

Use CASE WHEN to bucket employees into salary bands, and inside COUNT() to conditionally tally rows.

Common Table Expressions (CTEs) With WITH

cte

Use a WITH clause to compute total spend per customer as a named, reusable result set, then filter and join against it.

Ready to write your first query?

Jump into the interactive playground and start running real SQL against sample databases — right now, in your browser.

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