Re: How to structure applications using a RDBMS

[gav^]

You might want to look at two cunning modules by Michael Schwern/Tony Bowden, Ima::DBI and Class::DBI. The first gives all your classes nice cached DBI handles and SQL statements. In your class you set up your SQL statements:

   My::User->set_sql(
      'getUsers', 'select * from users', 'Main'
   );

Which you can then retrieve in anything that uses the class:

   my $sth = My::User->sql_getUsers;
   $sth->execute();
   # etc

I like this approach because all the SQL lives in a seperate module and doesn't mess up your main application. It also has some handy shortcuts like:

    $sth->execute([qw/value1 value2/], [\my $res1]);
    my %hash = $sth->fetch_hash;

Now Class::DBI is a great abstraction layer if, like me, you don't like to play with SQL at all. An example:

package User;
use base 'Class::DBI';

User->table('users');
User->columns('All', qw/id name password/);
User->coumns('Primary', 'id');
User->set_db('Main', 'dbi:mysql', 'gav', 'perlmonks');

Now like magic you have a class to talk to the database and hide you from the horrors of SQL:

    my $user1 = User->new({ name => 'gav', password => 'monk' });
    my $user2 = User->retrieve(1023);
    printf "Id: %d, Name: %s, Pass %s\n", $user2->id, $user2->name, 
        $user2->password;

or

    my $user = User->search(name => 'gav');
    if ($user && ($user = $user->next) && $user->password eq 'monk') {
        print "Welcome gav^!\n";
    } else {
        print "Schoo!\n";
    }

This came out a bit longer than I expected, but I hope it might help somebody :)

gav^