If you are using VPCart 7.xx, please jump to this helpnote :
http://helpnotes.vpasp.com/kb/604-Tips-and-Tricks-for-Version-8/993-How-to-run-multiple-sites-on-the-one-database-in-VPASP-70/
If you are using VPCart 8.xx, please jump to this helpnote :
https://helpnotes.vpcart.com/kb/10-VP-ASP-Shopping-Cart/1230-How-to-run-multiple-sites-on-one-database-in-VPCart-v8/
Using VPCart (v9) you can run more than one shop in one database. Each can share products and have products that are unique to them.
Assume you already have 1st site running, and you want to setup 2nd site, 3rd site etc. with latest VPCart, you can follow the user guide chapter below:
https://helpnotes.vpcart.com/userguide900/#!Documents/runtwoormoreshopsofftheonedatabaseproductmatching.htm
Good luck!