Ah, I should have been clearer in my initial response. I actually have no opinion on whether zip codes are a number, as I'm from the UK and don't really know ho

Ah, I should have been clearer in my initial response. I actually have no opinion on whether zip codes are a number, as I'm from the UK and don't really know how they work :-). I was more responding to the idea that any numeric value you don't do calculations on should be stored as a bare string. I would be happy enough with a string that had a constraint limiting the string to characters [0-9], though (again, assuming the data in question is limited to those chars). On the whole, pgexercises punts on the data modelling aspect, as it's focused on teaching SQL instead - in some cases choosing deliberately bad schema design to make it easier to ask interesting questions. On reflection I'm not sure this was a good approach, but I'm far past the point where I have time/inclination to revisit it.