Forget passive video courses. Seaquel's built-in tutorial puts you in front of a real database from the first minute. Write queries, see results, and build confidence through hands-on practice.
No theory overload. Each lesson gives you a goal, a real database, and a place to write SQL. You learn by doing.
Start with SELECT and work your way up to JOINs, aggregations, subqueries, and window functions. Each lesson builds on the last.
Drag and drop tables onto a canvas and connect them visually. See how SQL clauses map to what you build — it makes JOINs click.
A free-form playground with a sample e-commerce database pre-loaded. Experiment with any query — no risk, no setup, instant results.
A structured curriculum that takes you from your first query to writing advanced SQL with confidence.
Read the explanation, then run the queries yourself. Each lesson works on its own, so you can start anywhere.
What SQL actually does, the four tables you'll be querying throughout this course, and your first working query. No setup, no install, no signup.
Choosing columns, renaming them, computing new ones, removing duplicates and limiting results. Plus the evaluation order that explains most beginner errors.
Comparison operators, AND/OR precedence, IN, BETWEEN, LIKE, and the NULL behaviour that makes WHERE quietly drop rows you expected to see.
Sorting on one column or several, ascending and descending, where NULLs land, and why a query without ORDER BY has no guaranteed row order at all.
COUNT, SUM, AVG, MIN and MAX, the difference between COUNT(*) and COUNT(column), and how aggregates quietly skip NULLs in a way that can skew an average.
How GROUP BY buckets rows before aggregating, why every non-aggregated column must be grouped, grouping on multiple columns and on expressions.
WHERE filters rows before grouping, HAVING filters groups after. The difference, when each one is correct, and why using the wrong one changes your numbers.
INNER, LEFT, RIGHT and FULL joins with working examples, plus the two mistakes that quietly corrupt results: filtering a LEFT JOIN in WHERE, and row fan-out.
Queries inside queries: scalar subqueries, IN and EXISTS, correlated subqueries, and the NOT IN behaviour with NULLs that returns zero rows for no obvious reason.
WITH turns nested subqueries into named steps you read top to bottom. Chaining CTEs, when they help, when they hurt performance, and a short note on recursion.
OVER, PARTITION BY and ORDER BY, the difference between ROW_NUMBER, RANK and DENSE_RANK, running totals, LAG and LEAD, and how to filter on a window result.
The full schema and sample data behind this course, a set of exercises from easy to hard, and a sandbox to run any query you like against it.
Stuck on an error message? See common SQL errors and how to fix them
This is the real app running in your browser. Click below to open the interactive SQL tutorial.
Click anywhere to start exploring ·
The tutorial runs right inside Seaquel — practice on sample data, then switch to your own database and apply what you've learned. Download for the full experience.