What data modelling tool is sufficient for a student learning database design?

Disclaimer: I do not intend this to be a question based on opinion and start data wars (I don't know if such things exist in this realm unlike software development and programming languages) What I want: I want a piece of software (hopefully free, I am a student) that does not necessarily have to come with all the bells and whistles of professional data suites, but one that will allow me to: - create ERDs - design my databases, tables, fields, - create primary keys, link foreign keys - visualize relations b/w tables Most of what I have found such as erwin Data Modeler have free trials only. Once again, its not about the bells and whistles since I am what you could call a beginner. I have a personal desktop app I am working on and I don't want to keep looking at the code to remember the tables nor keep opening SQLITE DB Browser. Any sense of direction would be appreciated.