Each domain will come with 1 MySQL Database. If you are looking to have multiple subdomains?, then your CMS platform has probably already assumed such, and you can identify a table prefix. For example, the table prefix for this website is host_. Since a domain will only need 1 database, it would be simple to use this particular method with subdomains that I described. If you were to acquire a new domain, then that domain will have a unique MySQL database. All databases URL? will be sql.you.tld.