Would should write de select statement as follow:

select * from FeedDatabase inner join BpDatabase on FeedDatabase.[fieldname1] = BpDatabase.[fieldname1]

On the ON part of your select statement you can put as many parameter you need but they have to exist in both table.

To make your select statement more readable you should use aliases, so the statement should looks like this:

select * from FeedDatabase FD inner join BpDatabase BD on FD.[fieldname1] = BD.[fieldname1]