An Animated Introduction to SQL – Learn to Query Relational Databases

In this tutorial, you’ll learn about the Structured Query Language (SQL), the standard language used to query relational databases. SQL is not a traditional programming language. In Python or Java, you write step-by-step instructions that tell the co…

In this tutorial, you’ll learn about the Structured Query Language (SQL), the standard language used to query relational databases.

SQL is not a traditional programming language. In Python or Java, you write step-by-step instructions that tell the computer exactly how to do something. This is called imperative programming.

SQL works differently. First, you understand what data is stored in your tables. Then you write a query describing what data you want and you give it to a database management system. The database management system figures out how to get it. This declarative style is part of what makes SQL powerful (and fun to use).

You don’t need to be a programmer to learn SQL, but having some programming experience helps. Concepts like conditional logic and comparing values to see if something is true or false will feel familiar if you’ve coded before.

If you want an introduction to the basics, check out some of my programming language tutorials listed below.

Tutorial Structure

This tutorial is built around three books of interactive code playbacks I use in my database courses:

Each section of this tutorial includes worked examples where I show how I write SQL step-by-step, explaining my thought process along the way. You’ll see me experiment, refine, and build queries piece by piece, just like a real developer would. I rely heavily on Entity-Relationship Diagrams and Schemas to help me visualize the data stored in the databases.

Here’s how the tutorial is organized:

Part 1: A Whirlwind Tour of SQL

(from Database Design and SQL for Beginners)

I start by exploring a simple database for a fictional pet adoption center called the Paw Prints Adoption Center. I introduce essential concepts like:

Entity-Relationship (ER) diagrams
Schemas
Table structure and relationships

This foundation sets the stage for everything that follows. If you’re new to database design, spend some time here before moving on.

Part 2: Core SQL Concepts and Keywords

(also from Database Design and SQL for Beginners)

I cover the most important SQL keywords and ideas. Each topic is explained in its own playback with examples:

CREATE TABLE, ALTER TABLE
SELECT, FROM, WHERE, JOIN
ORDER BY, GROUP BY, HAVING
INSERT, UPDATE, DELETE
Nested queries, Common Table Expressions, and set operations (UNION, INTERSECT, EXCEPT)
Indexes and transactions

This section works as a reference. If you’re stuck on a query or forget what a keyword does, come back here.

Part 3: Practice Problems

(from Worked SQL Examples)

Practice is how you really learn. I’ve included 36 practice problems using the Paw Prints database and a new university database. Each problem has an animated playback showing how I worked through the solution step-by-step.

Try writing your own query before watching the solution. Struggling with the problem first will help you learn much more than just watching me provide the answer.

These problems build your skills gradually and help reinforce the use of ER diagrams and schemas in real scenarios.

Part 4: Using SQLite in Programs

(from Programming with SQLite)

In this final optional section, I show how to connect SQL to real code. You’ll learn how to use the SQLite database in:

C/C++
Python and Flask
Java

Running Queries

A database management system (DBMS) is the software used to manage and query data in a database. Many DBMSs require significant configuration and often a separate server to respond to query requests. Setting these up can be challenging for newcomers.

SQLite is a simple DBMS that doesn’t require much setup. It’s a great tool to start with. It doesn’t need a standalone server and stores the entire database in a single file.

To make it easier to view and edit your databases, I recommend using DB Browser for SQLite. It’s a free, open-source tool with a simple interface and all of SQLite’s functionality built in. You can open database files, browse tables, run queries, and edit data using an intuitive user interface. It’s especially useful when you’re learning and want to quickly see how your queries affect the data.

Optional: Web-Based Alternative to DB Browser

If you prefer not to install any software, you can use a web-based tool like SQLite Viewer or SQLite Online. These let you upload a .sqlite file, run queries, and explore a database from your browser.

SQLite Viewer: A simple, read-only viewer. Good for inspecting tables and testing basic queries.
SQLite Online: A full-featured SQLite IDE. You can create databases, upload files, run queries, and even save your work.

Both tools are great for quick experiments or checking your work without installing anything.

Code Playbacks

This tutorial is not a traditional video or static text. Each section includes links to interactive code playbacks that animate how the code or query was built, step-by-step. You can pause and rewind to see each change as it happens.

Each playback includes a narrative, screenshots, whiteboard-style drawings, and self-grading multiple-choice questions to reinforce what you’ve learned.

If you haven’t seen a code playback before, don’t worry. They’re easy to use and allow you to see how queries evolve over time. Here’s a short video showing how to view a code playback:

Playback Press

Playback Press is the platform where I publish my interactive code walkthroughs. Each book includes step-by-step animations, AI tutoring, and built-in quizzes.

I also created Storyteller, the free, open-source tool that powers these playbacks.

AI Tutor

While you’re viewing a code playback, you can ask an AI tutor questions about the queries. It gives clear, focused answers and doesn’t rush you. You can also ask it to create new self-grading multiple-choice questions to test your understanding.

To use the AI tutor and quizzes, create a free account on Playback Press and add one of the books to your bookshelf.

Part 1: A Whirlwind Tour of SQL

When someone is asked to manage some data, most people’s first instinct is to use a spreadsheet. Spreadsheets are easy to use and flexible. But as your data grows more complex, they start to show some weaknesses.

One major issue is redundant data. When the same piece of information appears in multiple places, there’s a risk that one copy might change while the others stay the same. This can lead to inconsistencies, errors, and confusing results.

Relational databases help solve this by organizing data in a structured way that reduces redundancy by design. Before building a database, it’s helpful to model the data using an Entity-Relationship (ER) diagram.

Entity-Relationship Diagrams

An ER diagram is a planning tool used to visualize the structure of a database. It helps you figure out what kinds of data you need to store and how those pieces of data relate to each other.

Entities are the main objects or concepts in your system, like Person, Course, or Dog. Entities have attributes that describe them. A Person might have name, date of birth, and address attributes, for example.
Relationships describe how entities are connected. For example, a Person might adopt a Dog, or a Student might enroll in a Course.

By laying this out in a diagram, you can clearly see what data is being stored and how the entities are related to each other. This makes it easier to design the tables in your database correctly.

Here is an example of an ER diagram used in this part of the tutorial:

Schemas

A schema is another way to describe the structure of a database. It shows the same information as the ER diagram, but in a more technical and precise format focused on how the data will actually be stored. Each element of a schema will become a table in a database.

Instead of lines connecting boxes, a schema uses primary keys and foreign keys:

A primary key uniquely identifies each row in a table. Primary keys have a solid underline.
A foreign key refers to the primary key in another table, linking the two together. Foreign keys have a dashed underline.

Here is an example of a schema used in this part of the tutorial:

While an ER diagram is more visual and conceptual, a schema is more concrete and closer to the actual implementation in the DBMS. You’ll see both used throughout this tutorial as I move from planning to writing SQL.

Try It: Explore a Relational Database in Action

To see how these concepts work in practice, take a look at the following three code playbacks. They walk through the design of a relational database for a fictional pet adoption center called Paw Prints. These examples will help you understand how entities, relationships, and schemas come together in a real database and how to write simple SQL queries to explore that data.

Start with the first playback and move through all three in order:

Database Design and Simple SQL: Introduces the Paw Prints database and shows how to write basic SQL queries.
One-to-Many Relationships and More SQL: Covers one-to-many relationships and how to join related tables.
Many-to-Many Relationships and Even More SQL: Shows how to handle many-to-many relationships using join tables and more advanced queries.

As you watch, pause to make sure you understand how the data is structured and how each SQL query is written. You can always refer back to this section later if something in the next chapters isn’t clear.

Part 2: A Beginner’s Reference to SQL

This section takes a closer look at the core SQL commands introduced in the whirlwind tour. Each playback focuses on one topic and shows how to use it through step-by-step examples. I continue to use the Paw Prints database in these examples.

Think of this as a reference section. You don’t need to go through everything in order but you may want to go through them all at least once before beginning to practice in part 3. Come back here whenever you need a refresher on a particular SQL concept.

Here are the key concepts we’ll cover:

CREATE TABLE and ALTER TABLE

Learn how to define tables in a relational database. This playback shows how to create tables from scratch and how to change them later using ALTER TABLE.

INSERT

See how to add new rows of data to a table. This example shows how to use the INSERT command and make sure your data matches the table structure.

SELECT

This playback introduces the SELECT keyword in SQL. You’ll learn how to retrieve specific columns (or attributes) from a table and see what the result set looks like.

FROM

Explore how the FROM clause specifies which tables your data comes from. This sets the stage for combining data from multiple sources using a Cartesian product. You’ll also see how to JOIN tables together.

WHERE

Learn how to filter results using conditions. The WHERE clause helps narrow down the rows returned by a query. This playback also shows how to join tables by matching foreign keys to primary keys.

UPDATE and DELETE

Learn how to change existing data in the database with UPDATE and remove data using DELETE. You’ll also see how to avoid accidental changes by using WHERE conditions carefully.

ORDER BY

Sort your results using ORDER BY. You’ll learn how to control the order of your output using one or more attributes.

Aggregate Operators, GROUP BY, and HAVING

Group rows and calculate summary values using aggregate functions like COUNT, AVG, MIN, MAX, and SUM. This playback also shows how to use GROUP BY and HAVING to work with grouped results.

Nested Queries with IN and Common Table Expressions

Learn how to use nested queries – queries inside other queries – to build more flexible logic. This playback also shows how to write cleaner queries using Common Table Expressions (CTEs).

UNION, INTERSECT, EXCEPT

See how to combine the results of multiple queries. This example shows how UNION, INTERSECT, and EXCEPT help you work with data from different queries as if it were one set.

Transactions

Learn how to group multiple SQL commands into a single transaction, so they all succeed or fail together. Transactions help protect your data from partial updates.

CREATE INDEX

Improve query performance using indexes. This playback shows how to create an index on one or more columns and explains why that makes certain queries run faster.

Part 3: Practice Problems — Paw Prints and University Databases

Now it’s time to apply what you’ve learned.

Below are six practice problems that use the Paw Prints database from earlier examples. If you haven’t recreated it yourself, here is a link to the SQLite file dogsFinal.sqlite. Each one asks a specific question that requires you to write a SQL query to find the answer. Try solving each one on your own before watching the solution.

Don’t worry if you don’t get it right on the first try. Writing SQL often involves trial and error, even for experienced developers. The goal is to think through the problem and make progress, not to be perfect. Start small and build your queries up through an iterative process.

Click each link to view the playback after you’ve made your attempt:

Which Dogs Have Had the Most Visits?

Figure out how to count visits for each dog and sort them to find the most frequently visited ones.

Number of Adoptions and Average Age

Find the total number of adoptions and the average age of adopted dogs. You’ll need to filter the data appropriately.

Locations with Least/Most Aggressive Dogs

Use grouping to compare aggression levels across locations and determine where the most and fewest aggressive dogs are housed.

Average Time to Adoption By Location

Calculate the average time it takes for dogs to be adopted, broken down by location.

Finding Available Capacity at Each Location

Determine how much space is left at each shelter location by comparing total capacity to current occupancy.

Who Visited then Adopted an Aggressive Dog

This complex query asks you to track user actions over time, first visiting, then adopting an aggressive dog. A good challenge!

University Database

Next, you’ll work with a more complex database that models a university’s course and grading system. You’ll use it to analyze real-world relationships between students, professors, courses, and departments.

Download the SQLite version of the database here:
studentGrades.sqlite

Here are the entities in the database:

Students
Sections
Courses
Professors
Departments

And here are the relationships between them:

Each student takes zero or more sections. (Every student receives a grade.)
Each section has zero or more students taking it.
Each section is an instance of a course.
Each course has zero or more sections.
Each section is taught by a single professor.
Each professor teaches zero or more sections.
Each professor belongs to zero or more departments.
Each department has zero or more professors.
Each department has, at most, one professor who is its chairperson.
Each professor may chair, at most, one department.
Each course is offered by a department.
Each department offers zero or more courses.

The code playbacks highlight how I use ER diagrams and schemas to help me build my queries. You can preview them here:

Try each query on your own before watching the solution.

Part 4: Using SQLite in Programs

So far, you’ve learned how to write SQL queries and design relational databases. In this optional section, you’ll see how to use SQLite in actual code. Each playback walks through a working program that reads from and writes to a SQLite database.

Why Use SQLite in Programs?

SQLite’s simplicity makes it a great choice for quick projects, prototypes, and small applications. You don’t need to run a server, and everything is stored in a single file.

These playbacks show how to embed SQL directly into your code, so your programs can store and retrieve data as part of their normal workflow. I really love using it in my projects!

Here’s an overview of the playbacks:

C/C++

The C++ SQLite API

Shows how to set up and use the SQLite C++ API. You’ll open a database, run basic queries, and handle results.

An Object-Oriented Auction Program

Builds a more complex C++ program that tracks bids, items, and users. This example shows how to structure a real-world application with SQLite.

SQLite Transactions

Explains how to group multiple database operations into a single transaction. This protects your data from partial updates.

Python and Flask

Querying a SQLite Database

Connects a Python script to a SQLite database, runs queries, and processes the results using Python’s built-in libraries.

Creating SQLite Databases

Shows how to create new SQLite databases directly from Python, defining tables and inserting initial data.

Flask Basics

Introduces Flask. You’ll see how to build a simple web application that can serve pages and connect to your SQLite database.

Creating an API

Takes Flask further by creating a RESTful API that interacts with a SQLite database, letting you perform CRUD operations on a SQLite database.

Java

Using a SQLite Database in a Java Program

Shows how to integrate the SQLite driver into a Java application. You’ll learn how to open a connection, run queries, and handle exceptions properly.

Conclusion

By now, you’ve learned how to read and write real SQL. You’ve seen how to design a database, how to write queries that retrieve and modify data, and how to tackle increasingly complex questions using the tools SQL gives you.

If you worked through the practice problems you’ve already done what many developers do on the job: examine unfamiliar data, figure out the relationships, and write queries to answer real questions.

SQL is a skill that gets sharper the more you use it. Don’t worry if you still feel a little unsure. Repetition and exploration will build your confidence. Keep experimenting, break things, and try to fix them. That’s how you really learn.

If you’re planning to use SQL in your own projects, try building a small database from scratch or connecting SQLite to one of your programs. You’ll learn a lot by seeing what questions your own data brings up.

Thanks for reading. I hope these playbacks helped make SQL a little easier to understand. Good luck with your next SQL project.

Comments and Feedback

You can find all of these code playbacks and more in one of my free books:

Comments and feedback are welcome anytime: mark@playbackpress.com

​An Animated Introduction to SQL – Learn to Query Relational Databases

Tutorial Structure

Part 1: A Whirlwind Tour of SQL

Part 2: Core SQL Concepts and Keywords

Part 3: Practice Problems

Part 4: Using SQLite in Programs

Running Queries

Optional: Web-Based Alternative to DB Browser

Code Playbacks

Playback Press

AI Tutor

Table of Contents

Part 1: A Whirlwind Tour of SQL

Entity-Relationship Diagrams

Schemas

Try It: Explore a Relational Database in Action

Database Design and Simple SQL: Introduces the Paw Prints database and shows how to write basic SQL queries.

One-to-Many Relationships and More SQL: Covers one-to-many relationships and how to join related tables.

Many-to-Many Relationships and Even More SQL: Shows how to handle many-to-many relationships using join tables and more advanced queries.

Part 2: A Beginner’s Reference to SQL

Part 3: Practice Problems — Paw Prints and University Databases

University Database

Part 4: Using SQLite in Programs

Why Use SQLite in Programs?

C/C++

Python and Flask

Java

Conclusion

Comments and Feedback

An Animated Introduction to SQL – Learn to Query Relational Databases