The easy way to submit an InfoPath form to a database is to use the database template, which is going to submit all the data to the DB. Could you instead provide a view or some reports for the DB that your end users can see? If you have to only submit some data, you'll need to either write code or leverage a third party tool.
Do you use SharePoint? Maybe you would be able to promote just the data your end users would be interested in?
You can definitely submit via rules that include one rule to email the form and another to submit it to the DB.