Hi Jon, nice to see you back!
I think things are a little mixed up here. Databases and Domains are two very different things. I think some proper definitions from dictionary.com could clear this up better than I could:
Database
Code:
A collection of data arranged for ease
and speed of search and retrieval. Also called data bank.
Domain
Code:
In the Internet, a part of a naming hierarchy consisting of
a sequence of names separated by periods (dots) that corresponds
to the network number ...
... so a domain is an internet address while a database is a collection of data, in it's simplest form a database can be thought of as much like a spreadsheet.
You shouldn't have any problems using index.html rather than index.php but generally speaking you can create a file that contains only HTML and still call it index.php on most servers.