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, year
- table 'track' with columns: trackid, cd, title
+The database structure is based on the following rules:
+ An artist can have many cds, and each cd belongs to just one artist.
+ A cd can have many tracks, and each track belongs to just one cd.
-And these rules exists:
+The database is implemented with the following:
- one artist can have many cds
- one cd belongs to one artist
- one cd can have many tracks
- one track belongs to one cd
+ table 'artist' with columns: artistid, name
+ table 'cd' with columns: cdid, artistid, title, year
+ table 'track' with columns: trackid, cdid, title
+Each of the table's first columns is the primary key; any subsequent
+keys are foreign keys.
=head2 Installation
-Install DBIx::Class via CPAN should be sufficient.
-
-=head3 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,
- year TEXT
- );
-
- 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
-
-=head3 Set up DBIx::Class::Schema
-
-Change directory back from db to the directory app:
-
- cd ../
-
-Now create some more directories:
-
- mkdir MyApp
- mkdir MyApp/Schema
- mkdir MyApp/Schema/Result
- mkdir MyApp/Schema/ResultSet
-
-Then, create the following DBIx::Class::Schema classes:
-
-MyApp/Schema.pm:
-
- package MyApp::Schema;
- use base qw/DBIx::Class::Schema/;
- __PACKAGE__->load_namespaces;
-
- 1;
-
-
-MyApp/Schema/Result/Artist.pm:
-
- package MyApp::Schema::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' => 'MyApp::Schema::Result::Cd');
-
- 1;
-
+You'll need to install DBIx::Class via CPAN, and you'll also need to
+install sqlite3 (not sqlite) if it's not already intalled.
-MyApp/Schema/Result/Cd.pm:
+=head3 The database/tables/data
- package MyApp::Schema::Result::Cd;
- use base qw/DBIx::Class::Core/;
- __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
- __PACKAGE__->table('cd');
- __PACKAGE__->add_columns(qw/ cdid artist title year/);
- __PACKAGE__->set_primary_key('cdid');
- __PACKAGE__->belongs_to('artist' => 'MyApp::Schema::Result::Artist');
- __PACKAGE__->has_many('tracks' => 'MyApp::Schema::Result::Track');
+Your distribution already comes with a pre-filled SQLite database
+F<examples/Schema/db/example.db>. You can see it by e.g.
- 1;
+ cpanm --look DBIx::Class
+If for some reason the file is unreadable on your system, you can
+recreate it as follows:
-MyApp/Schema/Result/Track.pm:
+ cp -a <unpacked-DBIC-tarball>/examples/Schema dbicapp
+ cd dbicapp
+ rm db/example.db
+ sqlite3 db/example.db < db/example.sql
+ perl insertdb.pl
- package MyApp::Schema::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' => 'MyApp::Schema::Result::Cd');
+=head3 Testing the database
- 1;
+Enter the example Schema directory
+ cd <unpacked-DBIC-tarball>/examples/Schema
-=head3 Write a script to insert some records
+Run the script testdb.pl, which will test that the database has
+successfully been filled.
-insertdb.pl
+When this script is run, it should output the following:
- #!/usr/bin/perl
+ get_tracks_by_cd(Bad):
+ Leave Me Alone
+ Smooth Criminal
+ Dirty Diana
- use strict;
- use warnings;
+ get_tracks_by_artist(Michael Jackson):
+ Billie Jean (from the CD 'Thriller')
+ Beat It (from the CD 'Thriller')
+ Leave Me Alone (from the CD 'Bad')
+ Smooth Criminal (from the CD 'Bad')
+ Dirty Diana (from the CD 'Bad')
- use MyApp::Schema;
+ get_cd_by_track(Stan):
+ The Marshall Mathers LP has the track 'Stan'.
- my $schema = MyApp::Schema->connect('dbi:SQLite:db/example.db');
+ get_cds_by_artist(Michael Jackson):
+ Thriller
+ Bad
- my @artists = (['Michael Jackson'], ['Eminem']);
- $schema->populate('Artist', [
- [qw/name/],
- @artists,
- ]);
+ get_artist_by_track(Dirty Diana):
+ Michael Jackson recorded the track 'Dirty Diana'.
- my %albums = (
- 'Thriller' => 'Michael Jackson',
- 'Bad' => 'Michael Jackson',
- 'The Marshall Mathers LP' => 'Eminem',
- );
+ get_artist_by_cd(The Marshall Mathers LP):
+ Eminem recorded the CD 'The Marshall Mathers LP'.
- my @cds;
- foreach my $lp (keys %albums) {
- my $artist = $schema->resultset('Artist')->find({
- name => $albums{$lp}
- });
- push @cds, [$lp, $artist->id];
- }
- $schema->populate('Cd', [
- [qw/title artist/],
- @cds,
- ]);
+=head3 Discussion about the results
+The data model defined in this example has an artist with multiple CDs,
+and a CD with multiple tracks; thus, it's simple to traverse from a
+track back to a CD, and from there back to an artist. This is
+demonstrated in the get_tracks_by_artist routine, where we easily walk
+from the individual track back to the title of the CD that the track
+came from ($track->cd->title).
- 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,
- ]);
-
-=head3 Create and run the test scripts
-
-testdb.pl:
-
- #!/usr/bin/perl
-
- use strict;
- use warnings;
-
- use MyApp::Schema;
-
- my $schema = MyApp::Schema->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
-
-=head1 Notes
-
-A reference implementation of the database and scripts in this example
-are available in the main distribution for DBIx::Class under the
-directory F<examples/Schema>.
-
-With these scripts we're relying on @INC looking in the current
-working directory. You may want to add the MyApp namespaces to
-@INC in a different way when it comes to deployment.
-
-The F<testdb.pl> script is an excellent start for testing your database
-model.
+Note also that in the get_tracks_by_cd and get_tracks_by_artist
+routines, the result set is called multiple times with the 'next'
+iterator. In contrast, get_cd_by_track uses the 'first' result set
+method, since only one CD is expected to have a specific track.
This example uses L<DBIx::Class::Schema/load_namespaces> to load in the
appropriate L<Result|DBIx::Class::Manual::ResultClass> classes from the
C<MyApp::Schema::Result> namespace, and any required
L<ResultSet|DBIx::Class::ResultSet> classes from the
-C<MyApp::Schema::ResultSet> namespace (although we created the directory
-in the directions above we did not add, or need to add, any resultset
-classes).
+C<MyApp::Schema::ResultSet> namespace (although we did not add, nor needed
+any such classes in this example).
=head1 FURTHER QUESTIONS?
projects / dbsrgits/DBIx-Class.git / commitdiff