mysql> use test;
Database changed
mysql> show tables;
Empty set (0.00 sec)

mysql> create table nulltest (leeresfeld int(1) default null);
Query OK, 0 rows affected (0.02 sec)

mysql> insert into nulltest values (null);
Query OK, 1 row affected (0.01 sec)

mysql> select * from nulltest;
+------------+
| leeresfeld |
+------------+
|       NULL |
+------------+
1 row in set (0.02 sec)

mysql>\q
Bye
format_c@server:~> cd perl_scripts/
format_c@server:~/perl_scripts> vi test.pl
format_c@server:~/perl_scripts> cat test.pl && perl test.pl
use strict;
use DBI;
my $dbh = DBI->connect('DBI:mysql:database=test;host=localhost;','test','test')
        or die DBI::errstr();
my $sth = $dbh->prepare('SELECT * FROM nulltest') or die $dbh->errstr();
$sth->execute() or die $dbh->errstr();

my $i = 0;
while (my @row = $sth->fetchrow_array()) {
        print ++$i,"\n";
}
$sth->finish();
$dbh->disconnect();

exit;

1
format_c@server:~/perl_scripts>