Hi, I have queried two similar result sets from a database as hash reference. For matching rows, I need to subtract set1 - set 2 for columns 3 and 4. Thanks! Here is the code with the subset of data I queried: 

#!/usr/bin/perl
use DBI;
use DBD::mysql;

my $platform = "mysql";
my $database = "db_name";
my $host = "host_name";
my $port = "port_num";
my $tablename = "hist";
my $user = "user_name";
my $pwd = "pass";

open(STDOUT, ">C:\\perlscripts\\new.txt") || die "Can't open the file"
+;

my $dsn = "dbi:mysql:$database:$host:$port";
my $dbh = DBI->connect($dsn,$user,$pwd) || die "Could not connect: $DB
+I::errstr\n";

my $query = $dbh->selectall_arrayref("select cus,ta,sum(gd1) as gd1,su
+m(gd2) as gd2 from hist group by cus,ta order by cus", {Slice => {} }
+);

my $query2 = $dbh->selectall_arrayref("select cus,ta,sum(gd1),sum(gd2)
+ from current group by cus,ta order by cus", {Slice => {} });


foreach my $ref (@$query) {
   push(@{$arry}, join(",",$ref->{cus},$ref->{ta},$ref->{gd1},$ref->{g
+d2}))."\n";
}

foreach my $ref (@$query2) {
   push(@{$arry2}, join(",",$ref->{cus},$ref->{ta},$ref->{gd1},$ref->{
+gd2}))."\n";

[download]

Here is the subset of data I get from this code. For columns 3 and 4, I am basically subtracting set1 - set2 (if match is found in set2, otherwise just print set1). I don't know what approach will allow me to get to the results. What would be the right approach?? Thanks. 

set 1:            set 2:
Joe,A,85,90       Joe,A,80,85
Joe,B,80,99       Joe,B,70,90
Rob,A,50,70       Rob,A,40,70
Rob,B,60,65       Tim,A,70,89
Tim,A,87,89       Lou,A,30,51
Jon,B,82,92
Lou,A,30,51

Output:
Joe,A,5,5
Joe,B,10,9
Rob,A,10,0
Rob,B,60,65
Tim,A,17,0
Jon,B,82,92
Lou,A,0,0

[download]

In reply to array of arrays calculations by rocky13

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