I found this book to be very helpful, I'm not done yet but so far I'm really enjoying it.

"Perfectly intelligent programmers often struggle when forced to work with SQL. Why? Joe Celko believes the problem lies with their procedural programming mindset, which keeps them from taking full advantage of the power of declarative languages. The result is overly complex and inefficient code, not to mention lost productivity."

https://www.amazon.com/Joe-Celkos-Thinking-Sets-Management/d...

This book can help with getting into the right mindset: https://www.amazon.com/Joe-Celkos-Thinking-Sets-Management/d...

I really like Joe Celko. "Thinking in Sets" opened my mind up quite a bit.

http://www.amazon.com/Joe-Celkos-Thinking-Sets-Management/dp...