New
Pages
118
Published
2016
SQL Practice Problems
57 Exercises for Beginners Through Advanced SQL Users
Work through 57 carefully graded SQL problems and come away writing confident, correct queries against real-world schemas.
SQL Practice Problems gives you 57 hands-on exercises that build from simple SELECT statements to complex multi-table queries, window functions, and aggregation challenges. Each problem mirrors a task you'd actually face on the job, not a toy puzzle invented to test syntax. The problems escalate deliberately, so you develop real intuition for how the query engine thinks — not just how to copy patterns from a textbook.
About this book
Most SQL books spend the first hundred pages explaining concepts and leave you with a handful of contrived exercises at the end. SQL Practice Problems flips that ratio. The bulk of the book is problems — 57 of them, arranged from introductory to genuinely challenging — paired with clear, reasoned solutions that explain not just what the answer is but why it works.
The exercises use a consistent schema modeled on a realistic business database: orders, customers, products, employees, and suppliers. You work against the same tables throughout, which means you build genuine familiarity with the data rather than context-switching between unrelated toy datasets every few pages. That familiarity is exactly what separates someone who can answer interview questions from someone who can actually write production queries.
Problems are grouped into three tiers. Introductory problems cover filtering, sorting, and projection. Intermediate problems layer in joins, aggregation, grouping, and subqueries. Advanced problems push into multi-level aggregation, self-joins, correlated subqueries, and ranking. At each tier, the solutions model how an experienced analyst approaches a problem — choosing readable joins over nested subqueries when readability matters, knowing when a CTE clarifies intent, catching off-by-one errors in date ranges.
- 57 graded exercises with worked solutions and explanations
- Consistent real-world schema used throughout — no throwaway datasets
- Three difficulty tiers: introductory, intermediate, and advanced
- Solutions explain reasoning, not just syntax
- Focused on T-SQL and SQL Server, with most patterns applicable to any RDBMS
At 118 pages this is not a reference manual. It is a practice workbook. Read a problem, write your query, check your solution, understand the delta. Repeat. That loop, done 57 times, builds the kind of muscle memory that makes SQL feel natural rather than frustrating.
If you have read a SQL tutorial and still feel hesitant when a blank query editor opens in front of you, this book closes that gap.
🎯 What you'll learn
- Filter, sort, and project data accurately using WHERE, ORDER BY, and column expressions
- Join multiple tables confidently, choosing the right join type for the relationship
- Aggregate and group data to answer count, sum, average, and ranking questions
- Write correlated subqueries and understand when they cost more than a join
- Use self-joins to compare rows within a single table
- Apply date arithmetic correctly and avoid common off-by-one range errors
- Read a worked solution critically and diagnose why your own query differed
👤 Who is this book for?
- Developers who know basic SQL syntax but freeze when facing a real, ambiguous business question
- Data analysts transitioning from Excel or BI tools who need to write their own queries from scratch
- Students who have finished a SQL course and want structured, graded practice before entering the job market
- Professionals preparing for a technical interview that includes a SQL assessment
- Database newcomers who learn best by doing rather than reading explanations first
Table of contents
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01
Introduction and Setup
Get the practice database installed on SQL Server and understand the schema — tables, relationships, and sample data — so every subsequent exercise starts with a clear picture of the data model.
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02
Introductory Problems
Tackle the first tier of exercises covering SELECT, filtering with WHERE, sorting, and basic column expressions. These problems build comfort with the syntax before complexity is introduced.
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03
Introductory Solutions
Work through detailed solutions to each introductory problem, with explanations of why specific clauses were chosen and common mistakes to avoid.
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04
Intermediate Problems
Move into joins, GROUP BY aggregation, HAVING filters, and subqueries. These exercises reflect questions you would realistically encounter in a reporting or analytics role.
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05
Intermediate Solutions
Review fully explained answers to the intermediate tier, with attention to join order, null handling, and choosing between subqueries and derived tables.
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06
Advanced Problems
Face the hardest exercises in the book: multi-level aggregation, correlated subqueries, self-joins, and ranking tasks that require you to think carefully about set logic.
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07
Advanced Solutions
Examine worked solutions to every advanced problem, including alternative approaches and discussion of performance and readability trade-offs.
Frequently asked questions
Do I need any prior SQL experience to use this book?
You should already know what a SELECT statement is and have a rough idea of what joins do. The introductory problems are gentle, but this is a practice book, not a first introduction to SQL.
Which database system does the book target?
The exercises and solutions use T-SQL on Microsoft SQL Server. Most of the patterns transfer directly to other relational databases, but some syntax — date functions in particular — will differ if you use PostgreSQL or MySQL.
Where do I get the practice database?
The book directs you to download the Northwind database, a well-known Microsoft sample database that is freely available online. Setup instructions are included in the first chapter.
Is this book useful for interview preparation?
Yes. The problem format and difficulty progression map well onto the SQL portions of data analyst and junior developer interviews. The advanced tier in particular covers topics that appear frequently in technical screens.
At 118 pages, is there enough content to justify the purchase?
The value is in the problems and their explanations, not in page count. Working through all 57 exercises and genuinely understanding each solution typically takes several hours and builds skills that a 400-page reference book cannot.
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