How to retrive data from database for project input

Question

Hello friends in my project input to the project is database of any website for example an website like Ebay there are lots of user comes daily & purchase items.The database of this website is an input to my project & then my project find the frequently coming users & purchasing items.So anyone can help me how to take this database?,where is actual database?,where to put my project?On the web administrate
pc or on server. I am not going to take direct database of their sites I want to sell my project such a web sites then how i will  connect to database