DBIx::Class::Manual::Example(3)

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

  use strict;
  use warnings;

  use MyDatabase::Main;

  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

  use strict;
  use warnings;

  use MyDatabase::Main;

  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>