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

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


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

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

MyDatabase/Main.pm:




  package MyDatabase::Main;

  use base qw/DBIx::Class::Schema/;

  __PACKAGE__->load_classes(qw/Artist Cd Track/);

  1;

MyDatabase/Main/Artist.pm:


  package MyDatabase::Main::Artist;

  use base qw/DBIx::Class/;

  __PACKAGE__->load_components(qw/PK::Auto Core/);

  __PACKAGE__->table('artist');

  __PACKAGE__->add_columns(qw/ artistid name /);

  __PACKAGE__->set_primary_key('artistid');

  __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');

  1;

MyDatabase/Main/Cd.pm:


  package MyDatabase::Main::Cd;

  use base qw/DBIx::Class/;

  __PACKAGE__->load_components(qw/PK::Auto Core/);

  __PACKAGE__->table('cd');

  __PACKAGE__->add_columns(qw/ cdid artist title/);

  __PACKAGE__->set_primary_key('cdid');

  __PACKAGE__->belongs_to('artist' => 'MyDatabase::Main::Artist');

  __PACKAGE__->has_many('tracks' => 'MyDatabase::Main::Track');

  1;

MyDatabase/Main/Track.pm:


  package MyDatabase::Main::Track;

  use base qw/DBIx::Class/;

  __PACKAGE__->load_components(qw/PK::Auto Core/);

  __PACKAGE__->table('track');

  __PACKAGE__->add_columns(qw/ trackid cd title/);

  __PACKAGE__->set_primary_key('trackid');

  __PACKAGE__->belongs_to('cd' => 'MyDatabase::Main::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')->search({

      name => $albums{$lp}

    });

    push @cds, [$lp, $artist->first];

  }

  $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')->search({

      title => $tracks{$track},

    });

    push @tracks, [$cdname->first, $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 /],

        prefetch => [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 /],

        prefetch => [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 implentation 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.


TODO


AUTHOR


  sc_ from irc.perl.org#dbix-class

  Kieren Diment <kd@totaldatasolution.com>
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