Remove duplicate rows based on one column

I've a vista like this:

Agenzia    Codice Nome
Globmaster    012 NORTHWEST AIRLINES
Globmaster    020 LUFTHANSA CARGO
Globmaster    023 FEDERAL EXPRESS
Globmaster    024 EUROPEAN AIR EXPRESS EAE
Globmaster    988 ASIANA
Globmaster    994 LINEAS AEREAS AZTECA
Globmaster    995 B & H AIRLINES
Globmaster    997 BIMAN
Gabbiano  012 NORTHWEST AIRLINES
Gabbiano  020 LUFTHANSA CARGO
Gabbiano  023 FEDERAL EXPRESS
Gabbiano  400 PALESTINIAN AIRLINES
Gabbiano  406 UPS AIRLINES
Gabbiano  407 AIR SENEGAL INTERNATIONAL

I need to modify the query so that it won't give duplicate codes (Codice) at the result:

SELECT     'Gabbiano' AS Agenzia, Codice, Descrizione, FlBSP, MastroForn, CapocForn, ContoForn, SottocForn, CodIVANazAtt, CommNazAttiva, CommIntAttiva, 
                      FlCancellato, DataUltModifica, IDUtente, IDTerminale, CodAnagrafico, NoteDirPortAnd, NoteDirPortRit, ImpDirPortPax, ImpDirPortVei, GGScad, 
                      PathCondGen
FROM         dbo.TVTV0000
UNION
SELECT     'Istantravel' AS Agenzia, Codice, Descrizione, FlBSP, MastroForn, CapocForn, ContoForn, SottocForn, CodIVANazAtt, CommNazAttiva, CommIntAttiva, 
                      FlCancellato, DataUltModifica, IDUtente, IDTerminale, CodAnagrafico, NoteDirPortAnd, NoteDirPortRit, ImpDirPortPax, ImpDirPortVei, GGScad, 
                      PathCondGen
FROM         IstanTravel.dbo.TVTV0000 AS Statistiche_1
UNION
SELECT     TOP (100) PERCENT 'Globmaster' AS Agenzia, Codice, Descrizione, FlBSP, MastroForn, CapocForn, ContoForn, SottocForn, CodIVANazAtt, 
                      CommNazAttiva, CommIntAttiva, FlCancellato, DataUltModifica, IDUtente, IDTerminale, CodAnagrafico, NoteDirPortAnd, NoteDirPortRit, ImpDirPortPax, 
                      ImpDirPortVei, GGScad, PathCondGen
FROM         Globmaster.dbo.TVTV0000 AS Statistiche_2
ORDER BY Codice

I don't even know why I get that silly TOP (100) PERCENT anyway ;)