Printers typically accept one of three inputs.. Text, PCL, or Postscript. I can't say I have ever seen a printer that accepts something different.
A printer wouldn't connect to any database. You need to query the database, format the output and send it to the printer.
We print barcodes using the Zebra printers like this
one
or the
Dymo Label Printers
well look at that I stand corrected..
Zebra XML enabled Zebra printers for Oracle connectivity
Learn something new every day...
Looks like there is a software XML solution as well that will work with many standard Label printers..
http://www.unibar.com/bc2000xml.htm
interesting..
Looks like XML printing was
patented by Toshiba in 2000 in the reference they mention the
Toshiba B-482 it either from 1999 or 2000, so that one is possibly pre 2000 ?