Databases / MEDIUM
Prepare for SQL interviews with 100 practice questions covering INNER/LEFT joins, GROUP BY, HAVING, subqueries, window functions, and CTEs.
Ace your next database engineer, data analyst, or backend developer technical interview with this 100-question SQL practice quiz. Designed to test practical query composition, relational logic, aggregation mechanics, and advanced analytic functions, this assessment covers the exact scenarios asked during technical coding screens.
The questions span essential and advanced ANSI SQL capabilities:
WHERE right.id IS NULL), RIGHT OUTER JOIN, FULL OUTER JOIN, CROSS JOIN (Cartesian products), and Self Joins; set operations (UNION vs UNION ALL deduplication overhead, INTERSECT, EXCEPT / MINUS).COUNT(*), COUNT(column) NULL behavior, SUM, AVG, MIN, MAX), GROUP BY multi-column grouping, filtering aggregates with HAVING vs row filtering with WHERE, and GROUPING SETS, ROLLUP, and CUBE.EXISTS vs IN performance), non-correlated subqueries, Common Table Expressions (WITH ... AS), and Recursive CTEs for traversing hierarchical data (organizational trees, category parent-child graphs).OVER (PARTITION BY ... ORDER BY ...), ranking functions (ROW_NUMBER(), RANK() with gaps, DENSE_RANK() without gaps), value functions (LAG() and LEAD() for period-over-period comparisons, FIRST_VALUE(), LAST_VALUE()), cumulative running totals, and frame specifications (ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW).INSERT INTO ... SELECT, UPDATE with joins, DELETE vs TRUNCATE (DDL vs DML, transaction rollback capabilities), foreign key constraints with ON DELETE CASCADE / SET NULL, unique constraints, check constraints, and default values.CASE WHEN ... THEN ... ELSE ... END, three-valued boolean logic (TRUE, FALSE, UNKNOWN), NULL comparison pitfalls (col = NULL vs col IS NULL), COALESCE() fallback resolution, and NULLIF().Every question presents schema definitions and SQL queries, challenging you to predict the exact returned rows, identify logical errors in join predicates, and optimize slow multi-table queries.
Standardized testing rules & scoring benchmarks
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