Where Is Sql ?

Hello,

I am very confused with this framework. So far I was working with CodeIgniter, but now my colleagues want me to start using Yii. I am reading the documentation and some things doesn't get any clearer to me.

First, after generating the basic application that gives us Log in system, I do not understand how it was made. I can not find any SQL, where is it ? Also when I use Gii to generate CRUD, again I can not find any sql.

I see that Yii have a lot of predefined methods and classes, but when I read documentation about them, I do not get any clearer how to use them and where.

Is there any book or guide that actually explains how to use this framework and what is going on here ? The Definitive Guide to Yii is not helping me at all to understand how to work with Yii.

Thanks