Can I rename a hash key inside another hash in Perl?

Question

I have a hash of a hash (HoH) that I got from using select_allhashref on a mysql query. The format is perfect for what I want and I have two other HoH by similar means.

I want to eventually merge these HoH together and the only problem (I think) I have is that there is a key in the 'sub-hash' of one HoH that has the same name as one in another HoH. E.g.

my $statement1 = "select id, name, age, height from school_db";
my $school_hashref = $dbh->selectall_hashref($statement1, 1);

my $statement2 = "select id, name, address, post_code from address_db";    
my $address_hashref = $dbh->selectall_hashref($statement2, 1);

So when I dump the data I get results like so:

$VAR1 = {
          '57494' => {
                       'name' => 'John Smith',
                       'age' => '9',
                       'height' => '120'
                     }
        }
};
$VAR1 = {
          '57494' => {
                       'name' => 'Peter Smith',
                       'address' => '5 Cambridge Road',
                       'post_code' => 'CR5 0FS'
                     }
        }
};

(this is an example so might seem illogical to have different names, but I need it :) )

So I would like to rename 'name' to 'address_name' or such. Is this possible? I know you can do

$hashref->{$newkey} = delete $hashref->{$oldkey};

(edit: this is an example that I found online, but haven't tested.)

but I don't know how I would represent the 'id' part. Any ideas?

Answer 1

Not knowing the way that you are merging them together, the easiest solution might be to simply change the select statement to rename the column in your results. Rather than trying to manipulate the hash afterward.

my $statement2 = "select id, name as address_name, address, post_code from address_db";    
my $address_hashref = $dbh->selectall_hashref($statement2, 1);

If that is not a realistic option for you then a loop might be your best option

foreach (keys %{$address_hashref}) {
  $address_hashref->{$_}{$newkey} = delete $address_hashref->{$_}{$oldkey}
}