SQL Quiz Book

A new kind of SQL quiz book that helps you visually understand how SQL works by connecting each query to the resulting changes in the table. Learn at your own level, from fundamentals to advanced concepts, with a focus on topics frequently encountered in real-world work.

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SQL Foundations

Learn querying through joins in order.

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Learn window functions and KPI analysis.

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106 quiz sets · 530 questions · 21 topics

Anomaly Detection4 sets · 5 questions each

Moving Averages, z-Scores1-1BASIC
Rankings, Cumulative Sums1-2BASIC
MAD, EWMA, Consecutive Runs1-1ADV
Rolling z-Scores, Signals1-2ADV

Batch Processing10 sets · 5 questions each

SELECT, JOIN, Aggregation1-1BASIC
UPDATE, Soft Deletes1-2BASIC
DISTINCT, NULLs, LIKE2-1BASIC
Window Functions, UPSERT2-2BASIC
CTEs, Window Functions1-1ADV
Running Totals and Pivots1-2ADV
UPSERT, Bulk Updates, Dedup2-1ADV
Soft Deletes and Pagination2-2ADV
Correlated Subqueries3-1ADV
LATERAL, JSONB, EXPLAIN3-2ADV

Behavioral Analytics4 sets · 5 questions each

Cohorts, Funnels, Churn1-1BASIC
Gaps and Islands1-2BASIC
Window Functions and CTEs1-1ADV
Attribution and RFM1-2ADV

Benchmarking4 sets · 5 questions each

Share, Growth Rates, Rankings1-1BASIC
Anti Joins and Moving Averages1-2BASIC
Multiple CTEs, FIRST_VALUE1-1ADV
LAG/LEAD, RANK, Scoring1-2ADV

Cardinality4 sets · 5 questions each

1:1, 1:N, and N:N Relationships1-1BASIC
LEFT JOIN and ROW_NUMBER1-2BASIC
EXISTS, LATERAL, Recursive CTEs1-1ADV
FULL OUTER JOIN and FILTER1-2ADV

CTE and WITH4 sets · 5 questions each

Query Cleanup and Refactoring1-1BASIC
Pre-Aggregation and Windows1-2BASIC
Multiple CTEs and Recursion1-1ADV
Multiple CTEs, Totals, RFM1-2ADV

Date and Time4 sets · 5 questions each

Ranges, Truncation, Gap Filling1-1BASIC
Month Ends, Zones, Elapsed Time1-2BASIC
Week Starts, Sessions, Averages1-1ADV
Merges, Workdays, Streaks1-2ADV

Deduplication4 sets · 5 questions each

DISTINCT, ROW_NUMBER, UNION1-1BASIC
DISTINCT, EXCEPT, INTERSECT1-2BASIC
DISTINCT ON and Window Functions1-1ADV
Set Operations and Windows1-2ADV

Event Modeling4 sets · 5 questions each

Sessions and DAU/MAU1-1BASIC
Funnels and Cohort Analysis1-2BASIC
Session IDs and Recursive CTEs1-1ADV
Attribution Analysis1-2ADV

GROUP BY4 sets · 5 questions each

Grouping, Aggregation, Conditionals1-1BASIC
DATE_TRUNC, STRING_AGG, Binning1-2BASIC
Pivots, Time Series, ROLLUP1-1ADV
COUNT DISTINCT, FILTER, ROLLUP1-2ADV

JOIN8 sets · 5 questions each

Joining Tables and Row Count Changes1-1BASIC
Join Types and Table Changes1-2BASIC
Join Patterns and Table Changes2-1BASIC
Multi-Table Joins and Table Changes2-2BASIC
Join Patterns and Row Count Changes1-1ADV
Subqueries and Join Patterns1-2ADV
Multi-Table Join Patterns2-1ADV
Complex Joins and Table Changes2-2ADV

JSON4 sets · 5 questions each

Extraction, Array Expansion, Containment1-1BASIC
Partial Updates, Building, Type Checks1-2BASIC
Recordsets, Path Queries, Rebuilding1-1ADV
Deep Merge, Diffs, Predicate Search1-2ADV

KPI Analysis4 sets · 5 questions each

DAU/MAU, CVR, and Retention1-1BASIC
Moving Averages, Mix, Churn1-2BASIC
Funnels, Cohorts, Pareto1-1ADV
MoM Growth, NTILE, Funnel CVR1-2ADV

NULL4 sets · 5 questions each

IS NULL, COALESCE, and LEFT JOIN1-1BASIC
Propagation, GROUP BY, FULL OUTER JOIN1-2BASIC
The NOT IN Trap, FILTER, LEFT JOIN1-1ADV
Aggregate NULLs, NULLIF, Zero Division1-2ADV

Performance Tuning12 sets · 5 questions each

EXPLAIN and Index Scans1-1BASIC
Composite Indexes, Joins1-2BASIC
Casts, LIKE, and OR/UNION2-1BASIC
NOT IN, NULL, Anti Joins2-2BASIC
Three-Valued Logic3-1BASIC
ROW_NUMBER and Casts3-2BASIC
Composite Indexes, Pre-Join1-1ADV
Covering Indexes and MVs1-2ADV
Index Design and LATERAL2-1ADV
Anti Joins, Sort Removal2-2ADV
LATERAL Top-N and Indexes3-1ADV
LAG/LEAD and Keyset Paging3-2ADV

Predicates4 sets · 5 questions each

Comparisons, BETWEEN, IS NULL1-1BASIC
IN/NOT IN and EXISTS1-2BASIC
IN Subqueries and ANY/ALL1-1ADV
LIKE, BETWEEN, and ANY1-2ADV

Recursive CTE4 sets · 5 questions each

Org Charts and Category Trees1-1BASIC
Series, BOM, Cycle Detection1-2BASIC
Graph Traversal, RBAC, BOM1-1ADV
RBAC, BOM, Double Recursion1-2ADV

Statistical Analysis4 sets · 5 questions each

Aggregates and Std Dev1-1BASIC
CORR, Regression, NTILE1-2BASIC
Rankings and Correlation1-1ADV
Residual Analysis1-2ADV

Subqueries4 sets · 5 questions each

Scalar, IN/NOT IN, and EXISTS1-1BASIC
NOT EXISTS and Correlation1-2BASIC
Correlation and Derived Tables1-1ADV
CASE, Multiple EXISTS, Nesting1-2ADV

Data Transformation4 sets · 5 questions each

CAST, COALESCE, and CASE1-1BASIC
Date Formats and Regex1-2BASIC
TO_CHAR and SPLIT_PART1-1ADV
LPAD/CONCAT_WS and REGEXP1-2ADV

Window Functions8 sets · 5 questions each

OVER, PARTITION BY, Totals1-1BASIC
LAG/LEAD, Moving Averages1-2BASIC
MAX/MIN OVER, FIRST_VALUE2-1BASIC
NTILE and PERCENT_RANK2-2BASIC
NTILE and FIRST/LAST VALUE1-1ADV
PERCENT_RANK and LAG+LEAD1-2ADV
Frame Clauses and Top-N2-1ADV
LEAD, FIRST_VALUE, WINDOW2-2ADV