Storing and displaying database content

I’m not sure what you’re trying to say. WordPress offers many options for setting up your own data types – both with and without programming. Depending on what this “register” is supposed to represent, there is probably already a suitable solution for it. Could you perhaps describe your project in more detail using a specific example?

I don’t think you need to. As I said, WordPress offers many possibilities without having to develop anything. Take a look at post types and taxonomies. These are data types that you can work with in WordPress – without having to do anything custom in the database.