while (my $ref2 = $sth2->fetchrow_hashref()) {
   my %tmp = %$ref2;
   while (my ($k, $v) = each %tmp) {
      $tmp{$k} = '' if (!defined $tmp{$k});
      $k = '';$v = '';
   }
   push @{ $tablist{$user_table} }, \%tmp;
}