Choose Your Level
Pick the difficulty that matches where you are. You can come back and try a harder level later.
Beginner
Write Basic Aggregation Queries
GROUP BY, HAVING, and ORDER BY on a sales table.
1 to 2 hours 3 criteria
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Intermediate
Window Functions for Ranking & Trends
ROW_NUMBER, LAG, and running totals on a time-series dataset.
2 to 3 hours 3 criteria
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Advanced
Optimize a Slow Query on a 50M-Row Table
Rewrite a query, add indexes, and explain the EXPLAIN plan.
3 to 5 hours 3 criteria
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