Professional SQL Server 2005 XML

I bought this book several months ago and was disappointed. One of the problem is that I am consistently debugging the codes. I am at Chapter 5 now and have spent numerous times googling to try to understand what is the correct syntex for some codes, such as using xml method for column-level contraints, which was demonstated in the book, but does not work. The other thing I don't like is the lack of explanation about the code examples. Many times, a code was throw out without clear explantion, such as how cross apply, outer apply works.