Not a book, but if you're looking to learn modern SQL in a hands-on way, I created Mastery with SQL (masterywithsql.com) specifically because I was frustrated with traditional SQL (and PostgreSQL) content that's lacking in high quality and challenging exercises.
Mastery with SQL has over 150 exercises, ranging from easy to very difficult, where you're primarily working with a single database and trying to answer interesting questions about a business (which months saw the highest revenue, best sales employee, most watched movie, find missing records, etc.).
I spent an enormous amount of time working on the exercises for this course (more than the actual content itself) and people who take the course consistently tell me working through the problems helped them learn SQL more deeply than they've learned anywhere else.
1. Like the other user asked, is it possible to adjust your prices for countries according to PPP? I was able to purchase Wes Bos's course like that for learning javascript and more.
2. How complex/difficult have your exercises evolve into? Can you give any examples?
I think there might be an issue with your FAQs section. I couldn't see the answers and it redirects me to "https://www.masterywithsql.com/#", taking me back to the top of the page.
Mastery with SQL has over 150 exercises, ranging from easy to very difficult, where you're primarily working with a single database and trying to answer interesting questions about a business (which months saw the highest revenue, best sales employee, most watched movie, find missing records, etc.).
I spent an enormous amount of time working on the exercises for this course (more than the actual content itself) and people who take the course consistently tell me working through the problems helped them learn SQL more deeply than they've learned anywhere else.