How do you handle migrations / SQL schema?

[fr3fou]

This project is exactly what I've been looking for in terms of architecture, however I'm trying to find a way to generate my SQL schema through the use of structs or something similar to that.

Right now what I have is a single variable that contains all of my CREATE TABLE statements and it's somewhat ugly. I was wondering what do you use, as I can't seem to find anything similar to that.