Perl DBI fetchall_hashref

问题

Consider the following table:

mysql> select * from vCountryStatus;
+-------------+------------+------+---------+--------+-----------------+
| CountryName | CountryISO | Code | Status  | Symbol | CurrencyName    |
+-------------+------------+------+---------+--------+-----------------+
| Brazil      | BR         |   55 | LIVE    | BRL    | Brazilian Real  |
| France      | FR         |   33 | offline | EUR    | Euro            |
| Philippines | PH         |   63 | LIVE    | PHP    | Philippino Peso |
+-------------+------------+------+---------+--------+-----------------+
3 rows in set (0.00 sec)

I am trying to construct a hash based on this table. For this I do the following:

#!/usr/bin/perl

use DBI;
use Data::Dumper;

my $dbh = DBI->connect("dbi:mysql:database=db", "user", "password", {RaiseError => 1, AutoCommit => 0, FetchHashKeyName => "NAME_lc"}) || die "DB open error: $DBI::errstr";

my $sth = $dbh->prepare("select * from vCountryStatus");
$sth->execute;
my $hash = $sth->fetchall_hashref('countryiso');
print Dumper($hash);

Here is the output this generates:

$VAR1 = {
          'PH' => {
                    'symbol' => 'PHP',
                    'status' => 'LIVE',
                    'countryname' => 'Philippines',
                    'countryiso' => 'PH',
                    'currencyname' => 'Philippino Peso',
                    'code' => '63'
                  },
          'BR' => {
                    'symbol' => 'BRL',
                    'status' => 'LIVE',
                    'countryname' => 'Brazil',
                    'countryiso' => 'BR',
                    'currencyname' => 'Brazilian Real',
                    'code' => '55'
                  },
          'FR' => {
                    'symbol' => 'EUR',
                    'status' => 'offline',
                    'countryname' => 'France',
                    'countryiso' => 'FR',
                    'currencyname' => 'Euro',
                    'code' => '33'
                  }
        };

The question is: why is the key of the hash (countryiso) repeated in the values inside the hash?

What I would prefer is the following output:

$VAR1 = {
          'PH' => {
                    'symbol' => 'PHP',
                    'status' => 'LIVE',
                    'countryname' => 'Philippines',
                    'currencyname' => 'Philippino Peso',
                    'code' => '63'
                  },
          'BR' => {
                    'symbol' => 'BRL',
                    'status' => 'LIVE',
                    'countryname' => 'Brazil',
                    'currencyname' => 'Brazilian Real',
                    'code' => '55'
                  },
          'FR' => {
                    'symbol' => 'EUR',
                    'status' => 'offline',
                    'countryname' => 'France',
                    'currencyname' => 'Euro',
                    'code' => '33'
                  }
        };

Is it possible using fetchall_hashref DBI method? Or do I have to go the traditional way, looping through each row and constructing the hash on the fly?

回答1:

No, it cannot be done using fetchall_hashref. But you can iterate over the hash values and delete the key:

delete $_->{countryiso} for values %$hash;

回答2:

I had this same problem but was using multiple keys on fetchall_hashref, so I had to go deeper in the hash references. Not exactly rocket science, but here it is:

(...)          
           my @keys=('key1','key2','key3');
           my $result_ref=$sth->fetchall_hashref(\@keys);

           remove_key_values($result_ref,\@keys);
(...)


sub remove_key_values {
    my ($href_values,$aref_keys) = (@_);

    foreach my $hk (keys %$href_values) {
        foreach my $ak (@$aref_keys) {
            if ($ak eq $hk) {
                delete $href_values->{$hk};
            }
        }
        if (exists $href_values->{$hk} and ref($href_values->{$hk}) eq 'HASH') {
                remove_key_values($href_values->{$hk},$aref_keys);
        }
    }
}

来源：https://stackoverflow.com/questions/3573370/perl-dbi-fetchall-hashref

标签

mysql

perl

dbi

hash