[Solved] How to inner join two tables?

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You say you want solutions in Python, MySQL or MongoDB. But you’ve tagged the question with “perl”. So here’s a Perl solution.

#!/usr/bin/perl

use strict;
use warnings;

my %file1 = get_file1();

open my $fh2, '<', 'File2' or die "File 2: $!\n";

chomp(my $header = <$fh2>);
print "$header\tcol_F\n";

while (<$fh2>) {
  chomp;
  my $colA = (split ' ')[0];
  print "$_\t$file1{$colA}\n";
}

sub get_file1 {
  my %hash;

  open my $fh1, '<', 'File1' or die "File 1: $!\n";

  <$fh1>; # skip headers
  while (<$fh1>) {
    chomp;
    my ($key, $val) = split ' ';
    $hash{$key} = $val;
  }

  return %hash;
}

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solved How to inner join two tables?