#initial stuff
#...
build_hash($dbh, '', '', $href);

sub build_hash {
   my ($dbh, $field_str, $where_str, $href) = @_; 
   my $table_str = 'table_name';
   do {
         my @fields = qw( f1 f2 f3 f4 f4 f6 f7 f8 f9 );
         $field_str = join(', ', @fields);
   } unless $field_str;

   my $query = qq( select $field_str from $table_str );
   $query .= qq( where $where_str ) if $where_str;

   my $sth = $dbh->prepare($query)
         or die "Could not prepare '$query'\n";

   $sth->execute()
         or die "Could not execute '$query'\n";

   my $ct = 0;
   while (my $tmp_href = $sth->fetchrow_hashref) {
      $ct++;
      $$href{$ct} = $tmp_href;
   }

   $sth->finish
      or die "Could not finish '$query'\n";
}