Say I have a site - example.com

I also have a store section - shop.example.com

When I setup Google Analytics all the referals show as being from example.com which is to be expected since users will go there first and then, from there, enter shop.example.com

My question is, what is the easiest way to have google track it all as one domain?

I have been online looking for answers and have found a few articles on it - just wondering if I could gain any insight from my fellow sitepointers...

By the way, shop.example.com is running a 3rd party shopping cart shotware: zencart...

Any help would be appreciated.

I would imagine that quite a few people have this subdomain setup (with the store on shop.watever.com).