E-commerce database question

Hi all,

I don’t know if this is the right place to post this, if it’s not could someone point me in the right direction.

I am building an e-commerce web site and have a few questions I can’t find answers too.

If I use a PHP script for a customer to add their e-mail address to a mailing list, how would I store this info. Would it be on a MYSQL database (hosted on a Linux server) or another database? How would the database be created?

Same sort of question, if I used a PHP shopping cart, what sort of database would I use to record sales details and how would it be created?

What is a flat database? As opposed too what other type?

Thanks

PieMan