Ask HN: Relational Databases and Concepts

Hi, I have never really dived into databases a lot, apart from some contact to SQL (wrote some select statements to extract some data, etc.) but I never fundamentally got into theory or on a conceptual level, i.e. an SQL database to me was just a set of tables that were kind of unhandy to work with. Until recently, when I touched Databases again (using Python SQLAlchemy's query language [not the ORM]). For the first time I was really exposed to the foreign-key concepts etc. and I think I saw quite some parallels to declarative languages such as Prolog, etc. All of the sudden I am eager to learn some more on the relational database concepts and I wonder where to find good material on that. Unluckily a lot of stuff I found on the web is in-the-trenches tutorials or get-yourself-started-with-php-mysql. I am especially interested in - design of good database schemas - refactoring of database schemas - best practices - conceptional treatment of database operations and their relation to