Database on Subdomain and Primary Domain

Hi,
I don’t know if it’s right if I ask here to all of you who can help me.

I have several wordpress related questions.

I have mydomain.com and want to create a subdomain with the name car.mydomain.com.

The contents of all content are actually the same except on my subdomain on car.mydomain.com only selling car products.

My question is:
1. Is it possible, when someone orders or registers an account on my subdomain, the order or their registration enters the mydomain.com database?
2. Do I use 1 databse which is used on mydomain.com and car.mydomain.com? Or do I have to have 2 databases?

By the way I use woocommerce for this. And I’m sorry if my English isn’t good enough.

thanks.