Is it possible to merge data frames with different amounts of rows?

[Mauri1313]

Hi! I have a little problem that I can´t solve. I have two data frames (DF): the first (Main DF) has 8 columns and 45918 rows, the second (Complementary DF) has 4 columns and 97969 rows. If you want to see the complete DF, here is the link to my GitHub: https://github.com/MauriAndresMU1313/Example_Merge_Dataframes Here an example that how look like the DF. Main DF:

 
ID1      ID2      dN     dS     Omega   Label_ID1       Label_ID2     
+  Group
AVP78042 AVP78031 0.0059 0.1188 0.0500  SARSr-bat-CoV   SARSr-bat-CoV 
+  Intra
ATO98108 AVP78031 0.1373 1.4673 0.0936  SARSr-bat-CoV   SARSr-bat-CoV 
+  Intra
ATO98108 AVP78042 0.1371 1.4224 0.0964  SARSr-bat-CoV   SARSr-bat-CoV 
+  Intra

Complementary DF:

 
Distance    ID_1        ID_2        Value
DISTANCE    AVP78042.1  ATO98108.1  0.29731
DISTANCE    AVP78042.1  ATO98120.1  0.29281
DISTANCE    AVP78042.1  ATO98132.1  0.33095

In this case, my main goal is to merge the complementary´s columns (ID_1, ID_2 and Value) to the main DF. The ID_1 and ID_2 in both cases are the same, however, have a different order. To do that, I think in to do a match between ID_1 and 2 between both data frames and when the match is true to add the column Value (Complementary DF) to the Main DF. I think in an "if" condition to do that. The problem here maybe is the different amount of rows and the order of the labels (ID_1 and ID_2) between each DF. Previously, I use a Perl script to merge DF:

use strict;
use warnings;
use feature qw{ say };

sub load {
    my ($file, $table, $phase) = @_;
    open my $in, '<', $file or die "$file: $!";
    while (<$in>) {
        chomp;
        my @columns = split /\t/;
        my $id = join '_', @columns[0, 1];
        die "Duplicate $id."
            if 'first' eq $phase && exists $table->{$id};

        push @{ $table->{$id} }, $columns[2];
        say join "\t", @columns[0, 1], @{ $table->{$id} }
            if 'print' eq $phase;
    }
}

my %table;
my $phase = 'first';
while (my $file = shift @ARGV) {
    load($file, \%table, $phase);
    $phase = 1 == @ARGV ? 'print' : '';
}

I think to complete this script to work in my new goal, I need an "if" condition to generate a match between IDs. Here is an example of a possible output:

ID1          ID2         dN          dS          Omega   Value   Label
+_ID1       Label_ID2       Group
AVP78042     AVP78031    0.0059      0.1188      0.0500 0.29731  SARSr
+-bat-CoV   SARSr-bat-CoV   Intra
ATO98108     AVP78031    0.1373      1.4673      0.0936    -     SARSr
+-bat-CoV   SARSr-bat-CoV   Intra

I put the "-" in the column Value to show an example of "not match" between ID_1 and ID_2. I tried different ways, however, I can´t solve the problem yet. Any suggestion or comment to do that?