How to work with linked tables in Yii2 using ActiveRecord?

Question

Yii

Hello!
I am learning the Yii2 framework, I got to work with the database.
I generate CRUD using gii, the findModel function appears in the controller, in which there is such a request:
$model = Pages::findOne($id)
This line returns data from the table by ID.
I need to get data from a related table, I do this:

$model = Pages::find()
                ->leftJoin('content', '`content`.`page_id` = `pages`.`id`')
                ->where(['content.page_id' => $id])
                ->all()

But in this case, the data is selected only from the first table (you need to get the fields from the second one as well).
In this regard, 2 questions arise:
1. Is accessing the database in the controller generally normal? (I always thought that this is the prerogative of the model, but since it is implemented at the framework level? In general, I think I should transfer the logic I wrote to the model)
2. How to display the fields of the linked table? Somewhere you need to initially indicate that they exist? Help me to understand!
Thank you!

Answer 1

Create an association with the getContents() model. After that, you can access the attributes of the associated table through the relationship: $model->getContents()