my @all_fields = qw(ort mv_id mol_id);
# hier alle Felder, die Integer sein sollen
my @integer_fields = qw(mol_id); 

my @def_fields = ();
foreach (@all_fields) {
    push @def_fields, $_ if defined $params{$_};
}

for(@integer_fields){
    $params{$_} = undef if($params{$_} eq '');
}

if (@def_fields) {
    my $sql = "INSERT INTO recherche (" . join(',', @def_fields) . ") VALUES (" . join(',', ('?') x scalar @def_fields) . ")";
    my $sth = $dbh->prepare($sql) or die $dbh->errstr();
    $sth->execute(@params{@def_fields}) or die $dbh->errstr();
}