What are good learning resources for design database models ?
A good starting point would be to look at Database normalization. Good db design is a job in itself… But You start can small by knowing how to model associations.
If You know how to design has_one, belongs_to, has_many, many_to_many, self referential join etc. You are good to go.
Often the framework will abstract the database layer, so You don’t need to care which one You will be using. Changing db should be as simple as changing config.
Later You might need to optimize your db, replicate data, use window functions, use views etc. It is also good to know how to import/export with sql commands. This should be done with your db tools, not the framework tools.
Six-Step Relational Database Design It helped me. I was avoiding new tables, because i was thinking that is performance issue. But that was a mistake.
@kokolegorille as you told database normalization more important topic than i imagined.