QuerydrillDrill the SQL interviews actually ask.
60 exercises on real tables, including Work mode tasks on messy data. Checked on your result, not your wording, and on changed data too, so guesses fail.
Checked twice, like a real reviewer would.
- 01Write the querySee the sample tables, type SQL, run it as often as you like.
- 02It runs on two datasetsThe sample data, and a copy with new rows and changed values.
- 03You learn whyIt names the mistake: a join that duplicates rows, an inner join that drops them, integer division, a typed-in value. Hints and a worked solution follow.
Six levels, from first SELECT to real work on messy data.
| 12 | Basics | SELECT, WHERE, ORDER BY, LIMIT, DISTINCT, IN, LIKE, NULL handling and CASE. |
| 13 | Aggregation | COUNT, SUM, AVG, GROUP BY, HAVING, COUNT DISTINCT and grouping by dates. |
| 12 | Joins | Inner, left and self joins, finding rows with no match, keeping zero counts. |
| 12 | Advanced | Subqueries, CTEs, RANK, DENSE_RANK, ROW_NUMBER, LAG and running totals. |
| 4 | Interview classics | Nth highest salary, earns more than the manager, pivots with CASE. |
| 7 | Work mode | Requests from Marketing, Finance and Support on messy tables: text amounts, mixed date formats, duplicates and stray spaces. |
Timed mode, like the live round.Each exercise gets a clock. Hints and solutions stay locked until time is up, and your best times are kept.
Start free. Pay once you are hooked.
Pro
- Every level, including window functions, CTEs and Work mode
- Worked solutions and explanations
- Progress and best times saved to your account
Payments open soon. The free exercises work now.
Questions
Which SQL does it use?
SQLite, running in your browser. The exercises stick to standard SQL that works the same way in PostgreSQL, MySQL and BigQuery, apart from the date function noted in the prompt.
Why did my query fail when the result looked right?
Every answer is also run on a changed copy of the tables with extra rows and updated values. A query that types in today's numbers or names passes the first run and fails the second. That is the same test an interviewer applies when they ask what happens if the data changes.
Do I need an account?
No. The free exercises work without one and save progress in your browser. A free account saves progress across devices, and Pro unlocks the rest.
How do I cancel the monthly plan?
Open Account and choose Cancel subscription. That is the whole process: you keep Pro until the end of the period you paid for and are not charged again. If Pro is not for you, you get a full refund within 14 days of paying.
What if my answer is right but marked wrong?
Answers are checked on the rows they return, not on how the query is written, so any correct query passes, and columns in a different order are accepted too. If a check still gets it wrong, use the report link under the result. Reports are reviewed, and a check that is wrong gets fixed.