I recently got a review for our “High Performance MySQL” book which was saying “What makes this book so much better than any others I’ve seen in the last 8 years is its focus on the why, rather than the how.”

This is the great note – it really goes back to how I wanted to see the book and to the principles we follow at Percona, helping our customers.

How –  this can be found as general advice and recipies.

Why –   is understanding how things internally work, laws and principles.

If you only know How == recepies but lack core understanding you may apply the recepies to the wrong situation and get stuck if it does not work (or go google for yet another recepie).    If you understand Why having deep understaning of how things work you can see which How to apply and if things do not work out as expected you will have the knowledge to modify your approach to solve the problem

Of course in the end you have to take an action which means you need to know How to do things.  How is important. However How without Why is shallow.