Leveling Up with SQL

A practical SQL guide from first queries to advanced data analysis techniques

Master SQL from your first SELECT to window functions and complex joins, and write queries you can trust in production.

Leveling Up with SQL takes you from basic data retrieval through the techniques that separate competent SQL writers from genuinely capable ones. You will build real queries against realistic datasets, understand why they work, and learn to spot the patterns that turn slow or broken SQL into something clean and correct. Whether you are just starting out or filling gaps in knowledge you use every day, this book gives you a structured path through the language.

Buy on Amazon →

About this book

SQL is everywhere, but most people learn it piecemeal: a tutorial here, a Stack Overflow answer there. The result is a working vocabulary with uncomfortable gaps. You can write a JOIN but you are not always sure which kind. You have heard of window functions but never quite reached for them with confidence. Leveling Up with SQL closes those gaps in order, from first principles to the features that unlock serious analytical work.

Author Mark Simon builds the material the way a good mentor would: start with what the database is actually doing, not just what syntax to type. Each chapter layers on the previous one, so by the time you reach subqueries, aggregation, and set operations, you understand why each tool exists and when to reach for it instead of an alternative.

The book covers the core SQL standard with attention to the dialects you are most likely to encounter day to day. You will spend time on SELECT, filtering, and grouping before moving into multi-table queries, then on to the advanced features that distinguish a strong analyst or backend engineer from someone who gets by. Worked examples stay grounded in realistic scenarios rather than toy data, so the patterns transfer directly to real work.

Filtering and sorting data precisely with WHERE, ORDER BY, and CASE
Joining tables correctly with INNER, LEFT, RIGHT, and FULL OUTER joins
Aggregating and grouping data with GROUP BY and HAVING
Writing readable subqueries and common table expressions
Applying window functions for ranking, running totals, and comparisons
Working with NULLs without being surprised by the results

If you write SQL regularly and want to feel fluent rather than functional, or if you are learning it properly for the first time, this is the structured practice you need.

🎯 What you'll learn

Write precise SELECT queries using filtering, sorting, and conditional logic from the ground up.
Join multiple tables correctly and choose the right join type for each situation.
Aggregate and group data with GROUP BY and filter aggregated results with HAVING.
Structure complex queries cleanly using subqueries and common table expressions.
Apply window functions to compute rankings, running totals, and period-over-period comparisons.
Handle NULL values predictably so your results are never silently wrong.
Recognise performance anti-patterns and write queries that hold up against real data volumes.

👤 Who is this book for?

Developers who use SQL day to day but want to move past copy-paste queries and understand what they are writing.
Data analysts and business intelligence practitioners who need stronger command of joins, aggregations, and window functions.
Students and career-changers learning SQL as part of a move into software engineering or data roles.
Backend engineers who interact with relational databases but never had formal training in the query language.
Anyone who learned SQL informally and wants a structured reference to fill in the gaps they know exist.

01

Getting Started with SQL

You set up a working environment and run your first queries, learning how a relational database stores and retrieves data and what the SELECT statement is actually doing.
02

Filtering and Sorting Results

You use WHERE, comparison operators, logical connectors, and ORDER BY to retrieve exactly the rows you need in the order you want them.
03

Working with Functions and Expressions

You apply scalar functions, string manipulation, date arithmetic, and the CASE expression to transform and label data inside a query.
04

Aggregation and Grouping

You summarise data with COUNT, SUM, AVG, MIN, and MAX, then control which groups appear in results using GROUP BY and HAVING.
05

Joining Tables

You connect data across multiple tables using INNER, LEFT, RIGHT, and FULL OUTER joins, and learn to diagnose the common mistakes that produce duplicates or missing rows.
06

Subqueries and Common Table Expressions

You restructure complex logic into readable subqueries and WITH clauses, understanding when each form is cleaner and when they are equivalent.
07

Window Functions

You use OVER, PARTITION BY, and ORDER BY inside window functions to compute running totals, ranks, and comparisons without collapsing rows the way GROUP BY does.
08

Advanced Techniques and Real-World Patterns

You work through set operations, NULL handling edge cases, and query patterns that appear repeatedly in analytics and application development, consolidating everything into production-ready habits.

Frequently asked questions

What prior knowledge do I need before reading this book?

No prior SQL experience is required. The book starts from the beginning and builds progressively, so complete beginners and readers with patchy existing knowledge will both find a clear path forward.

Which database system does the book use for its examples?

The examples follow standard SQL and are written to be broadly applicable. Mark Simon notes dialect differences where they matter, so the material translates to PostgreSQL, MySQL, SQL Server, and similar systems.

Is this book suitable for experienced SQL users, or is it mainly for beginners?

It is useful at both ends. Beginners get a structured introduction, while experienced users often find that chapters on window functions, CTEs, and NULL behaviour fill gaps they did not know they had.

Does the book include exercises or practice datasets?

The book includes worked examples throughout. Check the publisher page at Apress for any companion materials or code downloads associated with this edition.

When was this edition published, and is the content still current?

This edition was published in September 2023. SQL is a stable language, so the core content ages well, and the book reflects the features available in modern relational database systems.