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DBIx-Class-0.05999_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 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 DB
mkdir DB/Main

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

DB/Main.pm:

package DB::Main;
use base qw/DBIx::Class::Schema/;
__PACKAGE__->load_classes(qw/Artist Cd Track/);

1;

DB/Main/Artist.pm:

package DB::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' => 'DB::Main::Cd');

1;

DB/Main/Cd.pm:

package DB::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' => 'DB::Main::Artist');
__PACKAGE__->has_many('tracks' => 'DB::Main::Track');

1;

DB/Main/Track.pm:

package DB::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' => 'DB::Main::Cd');

1;

Write a script to insert some records.

insertdb.pl

#!/usr/bin/perl -w

use DB::Main;
use strict;

my $schema = DB::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 DB::Main;
 use strict;

 my $schema = DB::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 DB 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.  Please credit yourself properly!
Kieren Diment <kd@totaldatasolution.com>