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53 interactive SQL interview problems, organized by the concept they exercise. Pick the topic your target interview leans on, write queries against real seeded schemas, and get instant graded feedback.
INNER, LEFT, and multi-table joins - the single most-tested SQL skill in interviews.
3 free
GROUP BY, HAVING, and COUNT/SUM/AVG - turning raw rows into per-group answers.
4 free
Scalar and correlated subqueries - queries nested inside queries, evaluated per row or once.
ROW_NUMBER, RANK, LAG/LEAD, and running totals - the topic that separates senior candidates.
WITH clauses that name intermediate results - the readable way to build multi-step queries.
UNION, UNION ALL, and EXCEPT - stacking and diffing result sets.
Date filtering, truncation, and monthly rollups - where off-by-one bugs live.
WHERE, ORDER BY, LIMIT, and CASE - the warm-up questions every screen starts with.
6 free
CASE expressions, SUM(CASE ...) pivots, and value bands - conditional logic inside a query.
1 free
IS NULL, COALESCE, NULLs in aggregates, and the NOT IN trap - where correct-looking queries go wrong.
1 free
Pair the problems with the free SQL cheat sheets for syntax and performance patterns.