in reply to Database field names in code

For me, it's generally not a matter of hard coding the field names, but limiting the amount i do. When retrieving data for display, i strive to only "hard code" my database field names in 2 places ... the SQL query and the template (usually HTML). I discuss more of that in a moment, but for now, know that DBI allows you to deal with the query results in a variety of useful ways. You really should become familar with the documentation and then have a look into Class::DBI. For example, try this code on one of your SELECT queries: 

use DBI;
use Data::Dumper;

my $dbh = DBI->connect( ... );

# Example 1: List of Lists
print Dumper $dbh->selectall_arrayref('select id,name from status');

# Example 2: List of Hashes
print Dumper $dbh->selectall_arrayref(
 'select id,name from status',
 { Slice=>{} },
);

[download]
And pay close attention to the results. The first is really just a two dimensional table, like a spreadsheet without headers. Here is what my results yield: 
$VAR1 = [
          [
            '0',
            'enrolled'
          ],
          [
            '1',
            'dropped'
          ]
        ];
With this, i can now build a useful hash with which i can lookup values if need be ... but notice that i only specify the field names in the SQL query (and that i reversed them from the last example): 
my $rslt = $dbh->selectall_arrayref('select name,id from status');

my %hash = map @$_, @$rslt;

print Dumper \%hash;

[download]

But what about the second example, the one with the strange and cryptic { Slice => {} }? For a web developer who has to build reports and such, that is one of the best things since sliced bread. With this, i need only specify which fields i want in the SQL query, and then once more in the template. Here is an example that uses an easy to install CPAN module, HTML::Template. Just run the code first, you can ask more questions later. :) 

use DBI;
use HTML::Template;

my $dbh = DBI->connect(
   qw(DBI:vendor:database:host user pass),
   {RaiseError=>1},
);

my $things = $dbh->selectall_arrayref('
   SELECT id,name
   FROM status
',{Slice=>{}});

# optionally do more things to some of the fields
# yes, we do have to say their names again
$_->{id} = sprintf("%03d",$_->{id}) for @$things;

my $tmpl = HTML::Template->new(filehandle => \*DATA);
$tmpl->param(things => $things);

print $tmpl->output;

__DATA__
<tmpl_loop things>
   <tmpl_var id>: <tmpl_var name>
</tmpl_loop>

[download]

jeffa

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