Free ebook introducing SQL fundamentals: tables, SELECT queries, filtering, joins, aggregations, and practical database query patterns.
Free ebook content
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Relational Database Building Blocks
+ Exercise: Which approach best represents a many-to-many relationship between orders and products while also storing details like quantity and purchase price?
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Designing Tables with Keys and Relationships
+ Exercise: In a one-to-one relationship between users and user_profiles, what table design best enforces that each user can have at most one profile and that every profile belongs to an existing user?
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Reading Data with SELECT and Column Expressions
+ Exercise: Why is it usually better to list specific columns instead of using SELECT * in real work?
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Filtering Rows with WHERE and Logical Conditions
+ Exercise: Which WHERE clause correctly ensures the price rule applies to both conditions: the name contains refurb OR the category is Clearance, while also requiring price > 20?
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Sorting and Limiting Result Sets
+ Exercise: When building pagination queries, what is the main reason to add a unique tie-breaker column as the last item in ORDER BY?
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Combining Tables with Simple Joins
+ Exercise: You want to list all customers, including those with no orders, and show only orders with status SHIPPED when they exist. What is the correct way to apply the status filter?
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Summarizing Data with Aggregations and Grouping
+ Exercise: In a query that groups results by customer_id, how do you correctly keep only customers who have at least 5 completed orders?
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Practical Query Patterns and Common Pitfalls
+ Exercise: You need to return all orders, and include coupon details only when the coupon is active. Which JOIN and filter placement best avoids accidentally dropping orders with no coupon or an inactive coupon?
About the free ebook
SQL Fundamentals for Absolute Beginners (Any Database)
Build a practical foundation in SQL with this free ebook for people who want to understand and query relational databases. The lessons use concepts that transfer across popular database systems, helping you focus on the language and the reasoning behind effective queries.
Learn to work with relational data
Start with the building blocks of tables, rows, columns, keys, and relationships. You will see how thoughtful table design supports accurate data and makes it easier to retrieve meaningful results later.
Write useful SQL queries
Practice reading data with SELECT, shaping output with column expressions, and narrowing results with WHERE conditions. Learn how sorting and limiting results can make exploration faster and clearer.
Connect and summarize information
Understand how joins bring related tables together and how aggregate functions turn many records into useful totals, counts, averages, and grouped reports. The ebook also highlights practical query patterns and common mistakes to help you write more reliable SQL.
A database-neutral starting point
Examples emphasize core SQL ideas that are useful whether you later work with MySQL, PostgreSQL, SQL Server, SQLite, or another relational database. By the end, you will be able to read straightforward queries, create your own, and approach database questions with confidence.
- Understand relational database structure
- Filter, sort, and limit query results
- Use simple joins to combine related data
- Create grouped summaries with aggregations
- Recognize frequent SQL query pitfalls
Which SQL concepts are covered in this free ebook?
It covers tables, keys, relationships, SELECT, WHERE, sorting, joins, aggregations, grouping, and common query pitfalls.
Can I use these SQL lessons with MySQL, PostgreSQL, or SQLite?
Yes. The ebook focuses on core relational SQL concepts that apply across major database systems.
What is the difference between WHERE and GROUP BY in SQL?
WHERE filters individual rows before summarization, while GROUP BY organizes rows into groups for aggregate calculations.
This ebook includes:
8 content chapters
Digital certificate of course completion (Free)
Exercises to train your knowledge
100% free, from content to certificate
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