There are a few textbooks about this sort of stuff out there, when I was in college, we did this for a class project. This book should really help you on your way Database Systems: The Complete Book
I forgot to mention it, but my code is on googlecode here: cs4420-dbase
Please forgive the fact it is written in java, but I was outvoted by my teammates on that decision. but the basic ideas are all still there. It handles file creation and handling as well as a simple SQL parser and optimizer. It handles basic indexing (b-tree) and "memory" management. Please forgive some of the lack of commenting and strange commenting, many late nights were spent on that project.
