Assuming you have 3 seperate qvw's in 3 seperate folders, then you could simply put the 3 different include files into the 3 folders, with each file pointing to its respective database.
More elegant though is to have 3 dedicated folders for your 3 include files and use a relative path in your qvw to access them.
Instead of include I use mustinclude as that has error trapping should the file not exist.
