SQL Interview Prep, as a Game: The Proving Ground
The Proving Ground is an SQL interview prep game: three floors of timed drills modeled on real data interviews. Start on Floor 1, graduate to the advanced questions on Floor 3, then repeat until the patterns stop surprising you.
What a timed drill looks like
Every drill drops you into the same setup you get in a real screen: a schema panel, a question prompt, and a blank terminal. A countdown starts the moment the question loads, so there is no reading the problem for ten minutes before committing. You write a query, run it, and see your result grid immediately.
Answers are validated on the server against the expected result, not by string-matching your SQL. Any correct query counts, whether you solved it with a window function or a self-join. The client never sees the solution, so there is nothing to peek at: the only way through is to actually write the query. When the clock hits zero, the attempt is scored and you can retry for a better time.
That loop, question, countdown, submit, verdict, is what makes these timed SQL challenges feel like the real thing rather than homework.
The three floors
What the questions look like
Floor 1 targets beginner fundamentals: SELECT with filters, GROUP BY aggregation, basic joins, sorting and limiting. The kind of question used as a screener before an onsite. If you have written any SQL at all, start here to calibrate your speed.
Floor 2 is the intermediate tier: window functions, top-N per group, deduplication with ranking, self-joins, and the sort of aggregation gymnastics that separate strong candidates from candidates who memorized syntax.
Floor 3 is the advanced, senior-onsite tier: date gaps and islands, rolling aggregates, joins across three or more tables, and questions that force you to reason about the schema before typing anything. If you can clear Floor 3 under the clock, you are ready for almost any SQL screen.
Why a game beats grinding problem lists
Most people prepare by grinding problem sets, and most people stall the same way: they solve untimed, they re-read editorial solutions, and they never build the recall that interviews actually test. The Proving Ground works as a LeetCode alternative for SQL practice because it changes the two variables that matter. First, the timer: every question is solved under pressure, the same pressure you will feel with an interviewer watching. Second, the feedback loop: a server checks your result instantly, and stars reward speed and correctness together, so replaying a floor has a purpose.
It also does not feel like a chore. The Proving Ground sits inside SQL Protocol's spy fiction: each floor is a clearance level, each drill a live assessment. It reads less like an SQL quiz and more like an operation, which is exactly why people come back for one more run.
How scoring works
- Each question is timed. The timer starts the moment you begin.
- Stars are awarded for correctness and speed, not for the first pass alone.
- Hints are allowed but cost stars. Use them to learn, not to grind.
- Your best performance per question counts. You can revisit any floor to improve a score.
Companion guides
Our 15 SQL interview questions guide covers the same patterns in tutorial form. Read it as a warm-up, then drill under the clock here.
Frequently asked questions
What SQL questions are asked in data analyst interviews?
Most interviews cycle through a known pattern set: filtering and aggregation, joins across several tables, top-N per group, deduplication, date gaps, and window functions. The Proving Ground drills each of these under a timer, and our 15 SQL interview questions guide walks through the same patterns in tutorial form.
Is there a game to practice SQL interviews?
Yes. SQL Protocol's Interview Mode, the Proving Ground, is a free browser game built specifically for interview practice. You write real queries in a terminal against a countdown, and a server validates every answer. No install, no signup: guest mode starts instantly on desktop.
Is SQL Protocol's interview mode free?
Completely free. No credit card, no paid tier, no locked floors. Click and play as a guest, or sign in with Google if you want your scores and progress saved across devices. All three floors and every drill are available either way.
What difficulty levels are there?
Three floors. Floor 1 covers beginner fundamentals like filtering, aggregation, and basic joins. Floor 2 is intermediate: window functions, top-N per group, self-joins. Floor 3 is advanced, with gaps and islands, rolling aggregates, and multi-table reasoning at senior-onsite difficulty. You can replay any floor to improve a score.
Are the drills actually timed?
Yes. Every question runs against a visible countdown, and the timer is enforced server-side so it cannot be paused or tampered with. Timed practice is the point: interviews test recall under pressure, and an untimed editor never builds that. Your best time per question is what counts.
Drill the Proving Ground
Free, browser-based, no install. Play instantly as a guest, or sign in with Google to save your scores.