Marcus Ramberg > DBIx-Class-0.05999_04 > DBIx::Class::Manual::Example

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NAME ^

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

DESCRIPTION ^

This tutorial will guide you through the proeccess 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

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

 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

First, create some dirs and change working directory:

 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/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/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/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: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 scripts

testdb.pl:

 #!/usr/bin/perl -w

 use MyDatabase::Main;
 use strict;

 my $schema = MyDatabase::Main->connect('dbi:SQLite:example.db');

 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 ^

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 deployemnt.

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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