if not exists (select * from sys.systable tbl, sys.syscolumn clm where tbl.table_id = clm.table_id and 
               LCase(tbl.Table_Name) = LCase('Guests') and LCase(clm.Column_Name) = LCase('VisaN')) then
  alter table Guests add VisaN varchar(20);
end if;

go

update Registers
set Komentar = 'Reports=AllFGCards.qri
ReportBr=2
Report1=Karton1
Report2=Karton2
Variables+=
Karton1Osnovanie=Ianoaieoaeia caiiaaa
Variables-='

where RegisterName = 'AddressCardForeign' and 
  exists(select * from Registers where RegisterName= 'HotelId'
         and IntStojnost=44)