Hi Monks, I was looking for a solution to my problem of getting the top x matches for each error category, when I stumble upon the below example given by an expert. In my case, I already have the entire table stored in an array - @dataarray. I used a hash to get the count for each category. Colum 3 of the array holds the error code. The below is a simple code showing how I get the count for each category. 
my %error = (
    'disk' => 0,
    'cpu' => 0,
    'hdd' => 0,
    'graphics' => 0,
    'keyboard' => 0,
    '' => 0 #no error code
    );

for my $i (0 .. $#dataarray) {
    $error{$dataarray[$i][3]}++;
}

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Column 0 and column 1 holds the computer location and name (respectively). They are unique only as a pair. Can any experts advice how I can get the top x matches for each category? In addition, I also need the error occurance count for each of the top x computer location/name. Thanks. Nefertiti 
  my $query = $db->prepare("select code, username, userid from transac
+tions");
  $query->execute();
  my %code = map { $_ => [] } 0 .. 13;
  while (my $r = $qeury->fetchrow_hashref()) {
    my $c = $$r{code};
    push @{$code{$c}}, $r;
  }
  # For each code $c, $code{$c} is now an arrayref which
  # contains the relevant records (as hashrefs).  The
  # number of elements in the array equals the number
  # of occurances.  Now, for the second part...
  my %topfive;
  for my $c (keys %code) {
      my %user;
      for my $row (@{$code{$c}}) {
         # Note: this assumes that the userid field
         # is unique to each user.
         $user{$$row{userid}}{count}++;
         $user{$$row{userid}}{name} = $$row{username};
      }
      $topfive{$c} = [(sort {
        $$b[2] <=> $$a[2]
      } map {
        [$_, $user{$_}{name}, $user{$_}{count}]
      } keys %user)[0 .. 4]];     
  }

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In reply to Revisiting the "Getting top x matches" thread by nefertiti

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