Apex provides its own database layer, models and migrations but also has full interopability with Doctrie and Eloquent if you are familiar with and prefer either of those ORMs. To continue, click on the below links:
Apex Database Layer
Straight forward, easy to understand layer to access and manage the SQL database.
Create and manage your SQL database schema.
Model classes allowing you to easily retrieve and manage entities within the database.
Utilize Doctrine models and migrations.
Utilize Eloquent models and migrations.