As an aside, you should use strict - it makes it possible for Perl to tell you about typos in your code.

A while() loop never starts if the condition is false. You most likely want to use a different construct then, if you want your code to behave differently, or, if your database driver returns a reliable rowcount from the ->execute method, use that:

Variant 1 - database returns a reliable rowcount

my $count = $sth->execute;
if (! $count) {
    die "Couldn't execute >>$sql<< : " . $sth->errstr;
};
if ($count == 0) {
    print "No rows were affected.";
} else {
    while (my $pointer = $sth->fetchrow_hashref) {
    ... do magic ...
    };
};
[download]

Variant 2 - the DB driver does not return a reliable rowcount

my $res = $sth->execute;
if (! $res) {
    die "Couldn't execute >>$sql<< : " . $sth->errstr;
};

my $rows = 0;
while (my $pointer = $sth->fetchrow_hashref) {
    ... do magic ...
    $rows++;
};
if (! $rows) {
    print "No rows were affected.";
};
[download]