my @row;
while ( @row = $sth_C->fetchrow_array )
{

    undef @row;
}

##</code><code>##

    my $krow = join "\0", @row;

##</code><code>##

    $seen{$krow}++ and next;

##</code><code>##

    print OUTPUT_FILE join( "\t", @row ), "\n";