$all_rows = [
  [R1C1, R1C2, ..., R1Cn],
  [R2C1, R2C2, ..., R2Cn],
  ...,
  [RnC1, RnC2, ..., RnCn],
];

##</code><code>##

# Table: group
# Columns: id, name
# Values: 1, Admin
#         2, User
#         3, Public

my $sql = 'select * from group';
my $r = $dbh->selectcol_arrayref($sql); # default to first column

# or, if you want the the 'name' column
my @r = @{$dbh->selectcol_arrayref($sql, {Columns=>[2]})}; # we want the 2nd column

# if you know the column name you want in advanced:
my $sql2 = 'select name from group';
my @group_names = @{$dbh->selectcol_arrayref($sql2)};

print Data::Dumper->Dump(
  [$r, \@r, \@group_names],
  [qw(id name group_names)],
);


##</code><code>##

$id = [
        '1',
        '2',
        '3',
      ];
$name = [
          'Admin',
          'User',
          'Public',
        ];
$group_names = [
                 'Admin',
                 'User',
                 'Public',
               ];