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DBIx-Class-0.08198_01
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/ DBIx::Class::Manual::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
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>