Your query runs
Run returns the actual result set. You compare the rows you produced with the rows the question asks for, which is how you learn to spot a join that silently doubled them.
SQL practice on tables
that look like work.
39 questions in the CodeStory app, each on a real schema you can read before you write. Run the query, see the rows it returns, and find out whether it is right or only looks right.
Free to start: 100 AI credits when you sign up and 100 every month. Practice runs never cost credits.
Reading a query is easy. Writing one is not.
Most SQL rounds fail on the join, not the syntax.
You can follow someone else's SELECT and still stall when the question says "customers who ordered in March but not in April". The gap is not syntax. It is holding two tables in your head and knowing which join keeps the rows you need.
So every question opens with the schema: the tables, the columns, the types, which column is the primary key and which one points at another table. You read it the way you would read a real database, then write against it.
Questions carry a difficulty, a topic and a domain, so you can drill joins on their own, or window functions on their own, instead of hopping between unrelated puzzles.
Write it, run it, see the rows.
The editor behaves like a client, not like a text box.
A real verdict
Accepted, wrong answer, SQL error, timeout or limit exceeded. A query that works on ten rows and dies on a million fails here too.
Nothing is lost
Your query saves itself while you type, and it is mirrored in the browser, so a closed tab or a dropped connection does not cost you the work.
Mocks with a clock
Take a ready-made mock or build your own from the topics you pick, then sit it under time. Practice mode has no clock at all.
What the 39 questions actually cover.
Each question carries an estimated time, so you can plan a session that fits your evening.
SELECT and filtersthe round's first question
Joinsinner, outer, self
Group by and havingaggregates that lie
Subqueries and CTEswhen a join stops being enough
Window functionsranks, running totals
Schema design readswhat the tables imply
Where to go next.
The pages students open after this one.
Questions about sql practice.
Still not sure? Start free, or a mentor answers on a call.
Start freeIs SQL practice free?
The first ten questions are free. The rest open with the SQL pass, which is included from the Starter plan up.
Do I need to install a database?
No. The schema and the data live in the app, and your query runs against them in the browser.
Which SQL dialect is it?
Standard SQL as an interview asks it: joins, grouping, subqueries, CTEs and window functions. The questions avoid vendor-only syntax.
Can I practise under interview conditions?
Yes. Take a mock with a clock, or make your own from the topics you choose. Practice mode is untimed.
How long does a question take?
Each one shows an estimated time before you start, so you can fit a session into the time you have.
Not sure where to start? A mentor calls you, free.
Tell us who you are. On the call we help you pick the right batch.
- 1We check your level, from never coded to ready for interviews.
- 2We suggest online or campus, and a batch timing that fits your day.
- 3You decide. No pressure, no payment on the call.