Anything more recent by CJ Date. He was at IBM with EF Codd at the beginning of the development of the relational model. Try "Database in Depth: Relational Theo

Anything more recent by CJ Date. He was at IBM with EF Codd at the beginning of the development of the relational model. Try "Database in Depth: Relational Theory for Practitioners". It's good, when reading his stuff, to remember that SQL is a compromise to fit with a pure relational model, so you see things that make sense, but are not practical. Like choices for candidate keys, I suppose.