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DBIx::Class::Manual::Example.3pm

NAME

DBIx::Class::Manual::Example - Simple CD database example

DESCRIPTION

This tutorial will guide you through the process of setting up and testing a very basic CD database using SQLite, with DBIx::Class::Schema as the database frontend.

The database consists of the following:

   table 'artist' with columns:  artistid, name
   table 'cd'     with columns:  cdid, artist, title
   table 'track'  with columns:  trackid, cd, title
 
 

And these rules exists:

   one artist can have many cds
   one cd belongs to one artist
   one cd can have many tracks
   one track belongs to one cd
 
 

Installation

Install DBIx::Class via CPAN should be sufficient.

Create the database/tables

First make and change the directory:

   mkdir app
   cd app
   mkdir db
   cd db
 
 

This example uses SQLite which is a dependency of DBIx::Class, so you shouldn't have to install extra software.

Save the following into a example.sql in the directory db

   CREATE TABLE artist (
     artistid INTEGER PRIMARY KEY,
     name TEXT NOT NULL
   );
 
   CREATE TABLE cd (
     cdid INTEGER PRIMARY KEY,
     artist INTEGER NOT NULL REFERENCES artist(artistid),
     title TEXT NOT NULL
   );
 
   CREATE TABLE track (
     trackid INTEGER PRIMARY KEY,
     cd INTEGER NOT NULL REFERENCES cd(cdid),
     title TEXT NOT NULL
   );
 
 

and create the SQLite database file:

   sqlite3 example.db < example.sql
 
 

Set up DBIx::Class::Schema

Change directory back from db to the directory app:

   cd ../
 
 

Now create some more directories:

   mkdir MyDatabase
   mkdir MyDatabase/Main
   mkdir MyDatabase/Main/Result
   mkdir MyDatabase/Main/ResultSet
 
 

Then, create the following DBIx::Class::Schema classes:

MyDatabase/Main.pm:

   package MyDatabase::Main;
   use base qw/DBIx::Class::Schema/;
   __PACKAGE__->load_namespaces;
 
   1;
 
 

MyDatabase/Main/Result/Artist.pm:

   package MyDatabase::Main::Result::Artist;
   use base qw/DBIx::Class::Core/;
   __PACKAGE__->table('artist');
   __PACKAGE__->add_columns(qw/ artistid name /);
   __PACKAGE__->set_primary_key('artistid');
   __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Result::Cd');
 
   1;
 
 

MyDatabase/Main/Result/Cd.pm:

   package MyDatabase::Main::Result::Cd;
   use base qw/DBIx::Class::Core/;
   __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
   __PACKAGE__->table('cd');
   __PACKAGE__->add_columns(qw/ cdid artist title/);
   __PACKAGE__->set_primary_key('cdid');
   __PACKAGE__->belongs_to('artist' => 'MyDatabase::Main::Result::Artist');
   __PACKAGE__->has_many('tracks' => 'MyDatabase::Main::Result::Track');
 
   1;
 
 

MyDatabase/Main/Result/Track.pm:

   package MyDatabase::Main::Result::Track;
   use base qw/DBIx::Class::Core/;
   __PACKAGE__->table('track');
   __PACKAGE__->add_columns(qw/ trackid cd title /);
   __PACKAGE__->set_primary_key('trackid');
   __PACKAGE__->belongs_to('cd' => 'MyDatabase::Main::Result::Cd');
 
   1;
 
 

Write a script to insert some records

insertdb.pl

   #!/usr/bin/perl -w
 
   use MyDatabase::Main;
   use strict;
 
   my $schema = MyDatabase::Main->connect('dbi:SQLite:db/example.db');
 
   #  here's some of the SQL that is going to be generated by the schema
   #  INSERT INTO artist VALUES (NULL,'Michael Jackson');
   #  INSERT INTO artist VALUES (NULL,'Eminem');
 
   my @artists = (['Michael Jackson'], ['Eminem']);
   $schema->populate('Artist', [
      [qw/name/],
      @artists,
   ]);
 
   my %albums = (
     'Thriller' => 'Michael Jackson',
     'Bad' => 'Michael Jackson',
     'The Marshall Mathers LP' => 'Eminem',
   );
 
   my @cds;
   foreach my $lp (keys %albums) {
     my $artist = $schema->resultset('Artist')->find({
       name => $albums{$lp}
     });
     push @cds, [$lp, $artist->id];
   }
 
   $schema->populate('Cd', [
     [qw/title artist/],
     @cds,
   ]);
 
 
   my %tracks = (
     'Beat It'         => 'Thriller',
     'Billie Jean'     => 'Thriller',
     'Dirty Diana'     => 'Bad',
     'Smooth Criminal' => 'Bad',
     'Leave Me Alone'  => 'Bad',
     'Stan'            => 'The Marshall Mathers LP',
     'The Way I Am'    => 'The Marshall Mathers LP',
   );
 
   my @tracks;
   foreach my $track (keys %tracks) {
     my $cdname = $schema->resultset('Cd')->find({
       title => $tracks{$track},
     });
     push @tracks, [$cdname->id, $track];
   }
 
   $schema->populate('Track',[
     [qw/cd title/],
     @tracks,
   ]);
 
 

Create and run the test scripts

testdb.pl:

   #!/usr/bin/perl -w
 
   use MyDatabase::Main;
   use strict;
 
   my $schema = MyDatabase::Main->connect('dbi:SQLite:db/example.db');
   # for other DSNs, e.g. MySQL, see the perldoc for the relevant dbd
   # driver, e.g perldoc L<DBD::mysql>.
 
   get_tracks_by_cd('Bad');
   get_tracks_by_artist('Michael Jackson');
 
   get_cd_by_track('Stan');
   get_cds_by_artist('Michael Jackson');
 
   get_artist_by_track('Dirty Diana');
   get_artist_by_cd('The Marshall Mathers LP');
 
 
   sub get_tracks_by_cd {
     my $cdtitle = shift;
     print "get_tracks_by_cd($cdtitle):\n";
     my $rs = $schema->resultset('Track')->search(
       {
         'cd.title' => $cdtitle
       },
       {
         join     => [qw/ cd /],
       }
     );
     while (my $track = $rs->next) {
       print $track->title . "\n";
     }
     print "\n";
   }
 
   sub get_tracks_by_artist {
     my $artistname = shift;
     print "get_tracks_by_artist($artistname):\n";
     my $rs = $schema->resultset('Track')->search(
       {
         'artist.name' => $artistname
       },
       {
         join => {
           'cd' => 'artist'
         },
       }
     );
     while (my $track = $rs->next) {
       print $track->title . "\n";
     }
     print "\n";
   }
 
 
   sub get_cd_by_track {
     my $tracktitle = shift;
     print "get_cd_by_track($tracktitle):\n";
     my $rs = $schema->resultset('Cd')->search(
       {
         'tracks.title' => $tracktitle
       },
       {
         join     => [qw/ tracks /],
       }
     );
     my $cd = $rs->first;
     print $cd->title . "\n\n";
   }
 
   sub get_cds_by_artist {
     my $artistname = shift;
     print "get_cds_by_artist($artistname):\n";
     my $rs = $schema->resultset('Cd')->search(
       {
         'artist.name' => $artistname
       },
       {
         join     => [qw/ artist /],
       }
     );
     while (my $cd = $rs->next) {
       print $cd->title . "\n";
     }
     print "\n";
   }
 
 
 
   sub get_artist_by_track {
     my $tracktitle = shift;
     print "get_artist_by_track($tracktitle):\n";
     my $rs = $schema->resultset('Artist')->search(
       {
         'tracks.title' => $tracktitle
       },
       {
         join => {
           'cds' => 'tracks'
         }
       }
     );
     my $artist = $rs->first;
     print $artist->name . "\n\n";
   }
 
   sub get_artist_by_cd {
     my $cdtitle = shift;
     print "get_artist_by_cd($cdtitle):\n";
     my $rs = $schema->resultset('Artist')->search(
       {
         'cds.title' => $cdtitle
       },
       {
         join     => [qw/ cds /],
       }
     );
     my $artist = $rs->first;
     print $artist->name . "\n\n";
   }
 
 

It should output:

   get_tracks_by_cd(Bad):
   Dirty Diana
   Smooth Criminal
   Leave Me Alone
 
   get_tracks_by_artist(Michael Jackson):
   Beat it
   Billie Jean
   Dirty Diana
   Smooth Criminal
   Leave Me Alone
 
   get_cd_by_track(Stan):
   The Marshall Mathers LP
 
   get_cds_by_artist(Michael Jackson):
   Thriller
   Bad
 
   get_artist_by_track(Dirty Diana):
   Michael Jackson
 
   get_artist_by_cd(The Marshall Mathers LP):
   Eminem
 
 

Notes

A reference implementation of the database and scripts in this example are available in the main distribution for DBIx::Class under the directory t/examples/Schema.

With these scripts we're relying on @INC looking in the current working directory. You may want to add the MyDatabase namespaces to @INC in a different way when it comes to deployment.

The testdb.pl script is an excellent start for testing your database model.

This example uses ``load_namespaces'' in DBIx::Class::Schema to load in the appropriate Row classes from the MyDatabase::Main::Result namespace, and any required resultset classes from the MyDatabase::Main::ResultSet namespace (although we created the directory in the directions above we did not add, or need to add, any resultset classes).

TODO

AUTHOR

   sc_ from irc.perl.org#dbix-class
   Kieren Diment <kd@totaldatasolution.com>
   Nigel Metheringham <nigelm@cpan.org>