This is only good for extremely basic SQL queries. It has examples of every single query, so it's great as a reference, but it doesn't get into anything that's slightly complicated if you wanted to build your own database. However, I've heard that there are no good intro-to-SQL books, that's they're all way too easy, like this one, or they're way too difficult to understand. I guess I could give it three stars. It's an average book.