sub new_from_DBH{   #if you have already DBI connection, you can use this
    my ($pkg, $dbh, $param) = @_;

    my $self           = {};
    $self->{'DBH_OBJ'} = $dbh;
    $self->{'param'}   = {};

    foreach my $key(keys %{$param}){
      $self->{'param'}->{$key} = $param->{$key};
    }

    bless($self, $pkg);
    return $self;
}