my $dbh = DBI->connect("DBI:mysql:database=proyecto;host=localhost",
                         "root", "xyz123",
                         {'RaiseError' => 1});
   my $sth = $dbh->prepare("SELECT DISTINCT PAT FROM patentes");

$sth->execute();
   while ((my @row) = $sth->fetchrow_array()) {
   print "$row[0]\n";