Submit a query to compare outputs.
Solve SQL missions against a difficulty-based countdown timer. Beat the clock, match the expected result, optimize your query, inspect the execution path, and climb the local leaderboard.
Awaiting start
Press Start Countdown
Based on difficulty
Choose a challenge to begin.
Ctrl+Enter to submit.
Submit a query to compare outputs.
More remaining time earns more.
Lower query-plan cost earns more.
WHERE status = 'paid'
GROUP BY customer_id
ORDER BY total DESC
JOIN ... ON keys
Select only needed columns
EXPLAIN QUERY PLAN