It's easy to find information on SQL online. A simple search will overwhelm you with an avalanche of information.

When I worked at Expedia, I regularly interviewed people for jobs as database developers and data engineers. And I ran into an interesting situation. Applicants were asked to rank themselves on their SQL knowledge, on a scale of 1-10, with 10 being the highest (SQL expert).

Most applicants rated themselves at 9 or 10. In other words, they were experts. However, when I asked them to solve data problems by writing SQL, they couldn’t do it! And these weren’t hard problems—they were just a step above beginner level.

Why couldn’t they solve problems?

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The applicants were intelligent people, who had studied hard and had “book knowledge” on databases and SQL.

But when they were presented with a real-world problem, they had a very hard time. They just didn’t have the experience they needed to figure out how to handle a data problem.

It’s a “which came first: the chicken or the egg?” issue. In other words, it’s hard to get a data related job unless you have experience with SQL and other data tools. And it’s hard to get that experience unless you have the job.

The world of computer technology changes very quickly, and databases are no exception. The latest data-related buzzwords are data lakes, data science, the Internet of Things (IOT), data wrangling, machine learning, etc. Buzzwords that have been around a little longer are big data, cloud data, ETL, data analytics, dashboards, business intelligence, etc.

But...what basic, fundamental skill do you need, in order to work with any of these new database technologies? 

SQL! SQL is necessary for almost everything data related. Database systems have been around since the 1970’s and are used extensively at all companies and organizations. And to work with these databases at anything other than a very basic level, you need to understand and write SQL.

And unlike some other technologies and programming languages (which change very frequently), SQL is much more stable. Once you learn it, it’s a skill you can use for a lifetime.

You can watch videos online that will walk you through various aspects of databases, and SQL. And you can read up on SQL syntax and keywords, and review sample code.

But...

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You can do all of that, without absorbing much at all. Without absorbing the knowledge that will allow you to solve new problems on the job.

To really absorb and be able to apply your learning, you need to do real-world problems. Being presented with a SQL problem, and working through that problem (with hints, if necessary) will help you understand and remember concepts and principles like nothing else.

However, learning how to think through a data problem, break it down to the fundamentals, and craft an elegant, readable solution in SQL—that’s much harder to teach, and to learn.

It requires practice and experience. And most of the time, that level of practice and experience only comes from years of real world work with large datasets.

But by working though the carefully crafted problem sets in SQL Practice Problems, you can develop skills equivalent to those years of experience. And these skills will help you get the job you want.

It would have been easy to create a set of practice problems that just illustrate the main keywords in SQL.

Easy, but not useful.

Much more difficult to create, and much more valuable, are practice problems that cover the most common issues that you’ll encounter in your work with data. You can be sure that if a problem shows up in SQL Practice Problems, it’s one that will come up repeatedly in day-to-day work with data. Working through the problems will give you a very solid grounding in SQL.

SQL Practice Problems will teach you how to "think" in SQL, how to analyze data problems, figure out the fundamentals, and work towards a solution that you can be proud of. It contains challenging problems, that hone your ability to write high quality SQL code.

For most SQL training websites, the only payment option is a monthly subscription. And the only way to access the material is by logging in to their website. 

This works well for them. By not directly providing the learning material to you, they avoid the risk of copy/paste piracy. And many people forget to cancel the monthly subscription, even after they've stopped using it.

This is not what I do with SQL Practice Problems. You pay a one-time fee, and get lifetime updates. You get the full problem set, along with the complete instructions (with a video walk-through) for setting up the sample database. You work with the exact same tools that you would use in a work environment. 

With SQL Practice Problems, you’ll get experience solving some of the most common challenges you'll run into with data, and the best, most useful techniques to solve them.

It has data analysis and reporting oriented challenges that are designed to step you through introductory, intermediate and advanced SQL Select statements, with a “learn-by-doing” technique. The problems are business oriented, and use an order database. Working through the problems and absorbing the techniques presented—this is what will give you the skill and experience you need to solve real-life data problems.

Most SQL tutorials, textbooks, and courses have some practice problems. But they’re bloated. For the sake of completeness, most SQL keywords and syntax are included, even the useless ones. Studying these materials can be a massive waste of time.

SQL Practice Problems is different. Based on my years of experience working with data, I present those data problems that come up all the time. As the difficulty of the practice problems increases gradually, you’re continually challenged. The problems are unique and even fun—you can actually enjoy learning SQL!

Hi, my name is Sylvia Moestl Vasilik. I've been a senior data engineer, architect and database programmer for more than 15 years, working at top organizations like Expedia, Microsoft, T-Mobile, and the Gates Foundation. I write on database topics on my DatabasesAreFun blog.

A while back, I was teaching a SQL Server Certificate course with the University of Washington Professional Education program. It was a 10 week course, and my students paid more than $1000 for it. They learned the basics of SQL, most of the keywords, and worked through practice problems every week.

What was missing?

But I wasn’t really happy with what they were learning. Because of the emphasis on getting a overview of all features of SQL, we didn't spend enough time on the SQL that’s used 95% of the time—intermediate and advanced Select statements.

Yes, the students learned a lot about SQL. However, they spent a tremendous amount of money, and many hours every week, working through a dry manual, instead of solving real world data problems.

That's when I realized that there’s a desperate need for a set of practical, real-world SQL practice problems. Problems that will help people get the experience they need, for the jobs they want, packaged in an easy-to-follow, "learn-by-doing" format.

“An investment in knowledge always pays the best dividends.”

- Benjamin Franklin - 

​Learning sticks with you when you’re actually solving real problems, using the same tools you would use in a work environment.

Watching other people explain concepts on videos is fine for a shallow, introductory understanding. But you won't be able to solve problems.

Videos will not give you the hands-on experience that you need. For that, you need well-designed practice problems that teach data-oriented thinking through actual doing. Working through well-designed problems is the gold standard for learning.

Maybe you’ve tried and failed to get a better understanding of SQL, after multiple online courses and books. Many readers have emailed me, and said that they paid hundreds and even thousands of dollars for other educational materials that promised to teach SQL, that were—and this is a direct quote—"useless".

These materials were frequently just a reformatted version of the online documentation. Or they were extremely wordy, forcing them go through pages and pages of text to find anything useful.

They finally succeeded in learning SQL by working through these practice problems, step-by-step. This is what really helped them learn, and retain that learning.

In the standard version of both SQL Practice Problems and More SQL Practice Problems, most questions have numerous hints that you can use to move forward in solving the practice problem. They’re very useful if you’re completely stuck on a problem.

However, based on numerous requests from readers, I’ve created a special ‘no-hints’ version of the book.

But wait—not using the hints sound like more work! Why did my readers want this, and why do I now strongly recommend using this version? 

The latest research on brain function and learning teaches us that the more effort you need to put into solving a problem, the more deeply it sinks in. And the more easily you’re be able to solve new problems. 

In real life, when you’re trying to solve data problems, you won’t have handy, step-by-step hints that lead you to the answer. You’ll be able to search online for help—I always recommend this—but you won’t have hints like these. 

Learning at a deeper level...

So, to help you to learn at a deeper level—which involves a little more struggle—I also provide the ‘No-Hint’ version. 

I recommend printing out the No-Hint version, and working from that. Use the full version if you’re stuck. Or, you can do what some of my readers have done—use the full (hints included) version the first time around, and then go through the questions a second time, without hints, to test their learning. 

If you're buying the Basic package, you'll need a computer running Windows.

If you'd like to use SQL Practice Problems on a Mac, you'll need to purchase the Professional package, which includes the MySQL edition (as well as other features, including an additional problem set). MySQL can easily be installed on a Mac.

No. These practice problems involve only Select statements, used for data analysis, reporting, and business intelligence. It does not include modifying data (insert, delete, or update statements), or any kind of SQL programming, including stored procedures and functions. 

Why did I do this? Because Select statements are by far the most commonly used SQL. They're the most complex. And most importantly, they're the most difficult to get practice and experience in.

I thought about writing another book about SQL programming and modifying data, but I got only one or two customer requests for that.

Almost all my requests were for more practice problems, and more advanced practice problems, on Select statements. So that’s what I worked on, and put into the Professional package.

Cognitive research proves what we already know—that reading alone doesn’t get you much, either in terms of understanding and remembering, or being able to apply your knowledge.

But reading less, and doing more—being presented with a problem, and then asked to solve it – this changes things. You stay awake, and learning becomes more interesting. Maybe even fun! 

Let’s be honest—when you’re just reading text or watching videos, it’s easy to fool yourself into believing that you’re learning a lot more than you really are. 

But when you’re continually being challenged to solve problems, it keeps things real. You know for sure—either you can solve the problem, or you can’t. If you can’t solve the problem, you go back, maybe look at the hints, or look for help online. Then you try again. And once you’ve solved a practice problem in this book, you know you can solve it again, in real life.