=head1 NAME
DBIx::Class::Manual::Intro - Introduction to DBIx::Class
=head1 INTRODUCTION
So, you are bored with SQL, and want a native Perl interface for your
database? Or you've been doing this for a while with L<Class::DBI>,
and think there's a better way? You've come to the right place.
Let's look at how you can set and use your first native L<DBIx::Class>
tree.
First we'll see how you can set up your classes yourself. If you want
them to be auto-discovered, just skip to the next section, which shows
you how to use L<DBIx::Class::Loader>.
=head2 Setting it up manually
First, you'll need a base class. It should inherit from
L<DBIx::Class> like this:
package MyApp::DB;
use base qw/DBIx::Class/;
You will also want to load some of the L<DBIx::Class> components.
L<DBIx::Class::Core> provides a good starter set. In addition you'll
have to use either L<DBIx::Class::Schema> or L<DBIx::Class::DB>.
We'll use C<DB> in this introduction, since it involves less magic.
C<Schema> is mostly useful if you want to use multiple database
connections.
__PACKAGE__->load_components(qw/Core DB/);
If you want serial/auto-incrementing primary keys, you should use the
L<DBIx::Class::PK::Auto> component for your database. For example, if
you're using SQLite add C<PK::Auto::SQLite> to the list:
__PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
C<PK::Auto> classes exist for many databases; see
L<DBIx::Class::PK::Auto> for more information.
Once you've loaded the components, it's time to set up your
connection:
__PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
This method is similar to the normal L<DBI> C<connect> method, and can
take username, password, and L<DBI> attribute hash as well as the DSN.
With that out of the way, we can define our first table class:
package MyApp::DB::Album;
use base qw/MyApp::DB/;
Then we specify which table it uses,
__PACKAGE__->table('album');
and specify which columns it has.
__PACKAGE__->add_columns(qw/albumid artist title label year/);
This will automatically create accessors for each of the columns, so
that you can read/update the values in rows you've retrieved.
Also, you need to tell it which column is the primary key:
__PACKAGE__->set_primary_key('albumid');
If you have a primary key composed of multiple columns, just pass a
list instead.
That's pretty much all you need for a basic setup. If you have more
advanced needs like using more than one database connection for the
same class, see L<DBIx::Class::Schema>.
=head2 Using L<DBIx::Class::Loader>
This is an additional class, and not part of the L<DBIx::Class>
distribution. Like L<Class::DBI::Loader>, it inspects your database,
and automatically creates classes for all the tables in your database.
Here's a simple setup:
package MyApp::DB;
use DBIx::Class::Loader;
my $loader = DBIx::Class::Loader->new(
dsn => 'dbi:SQLite:/home/me/myapp/my.db',
namespace => 'MyApp::DB'
);
1;
This should be equivalent to the manual setup in the section above.
L<DBIx::Class::Loader> takes lots of other options. For more
information, consult its documentation.
=head2 Basic usage
Once you've defined the basic classes, either manually or using
L<DBIx::Class::Loader>, you can start interacting with your database.
The simplest way to get a record is by primary key:
my $album = MyApp::DB::Album->find(14);
This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause,
and return an instance of C<MyApp::DB::Album> that represents this
row. Once you have that row, you can access and update columns:
$album->title('Physical Graffiti');
my $title = $album->title; # $title holds 'Physical Graffiti'
If you prefer, you can use the C<set_column> and C<get_column>
accessors instead:
$album->set_column('title', 'Presence');
$title = $album->get_column('title');
Just like with L<Class::DBI>, you do an C<update> to commit your
changes to the database:
$album->update;
If needed, you can throw away your local changes like this:
$album->discard_changes if $album->is_changed;
As you can see, C<is_changed> allows you to check if there are local
changes to your object.
=head2 Adding and removing rows
To create a new record in the database, you can use the C<create>
method. It returns an instance of C<MyApp::DB::Album> that can be
used to access the data in the new record:
my $new_album = MyApp::DB::Album->create({
title => 'Wish You Were Here',
artist => 'Pink Floyd'
});
Now you can add data to the new record:
$new_album->label('Capitol');
$new_album->year('1975');
$new_album->update;
Likewise, you can remove it from the database like this:
$new_album->delete;
You can also remove records without or retrieving first. This
operation takes the same kind of arguments as a search.
# Delete all of Falco's albums
MyApp::DB::Album->delete({ artist => 'Falco' });
=head2 Finding your objects
L<DBIx::Class> provides a few different ways to retrieve data from
your database. Here's one example:
# Find all of Santana's albums
my $rs = MyApp::DB::Album->search({ artist => 'Santana' });
In scalar context, as above, C<search> returns a
L<DBIx::Class::ResultSet> object. It can be used to peek at the first
album returned by the database:
my $album = $rs->first;
print $album->title;
Or, you can loop over the albums and update each one:
while (my $album = $rs->next) {
print $album->artist . ' - ' . $album->title;
$album->year(2001);
$album->update;
}
For more information on what you can do with a
L<DBIx::Class::ResultSet>, see L<DBIx::Class::ResultSet/METHODS>.
In list context, the C<search> method returns all of the matching
rows:
# Fetch immediately all of Carlos Santana's albums
my @albums = MyApp::DB::Album->search({ artist => 'Carlos Santana' });
foreach my $album (@albums) {
print $album->artist . ' - ' . $album->title;
}
We also provide a handy shortcut for doing a C<LIKE> search:
# Find albums whose artist starts with 'Jimi'
my $rs = MyApp::DB::Album->search_like({ artist => 'Jimi%' });
Or you can provide your own handmade C<WHERE> clause, like:
# Find Peter Frampton albums from the year 1986
my $where = 'artist = ? AND year = ?';
my @bind = ( 'Peter Frampton', 1986 );
my $rs = MyApp::DB::Album->search_literal( $where, @bind );
The preferred way to generate complex queries is to provide a
L<SQL::Abstract> construct to C<search>:
my $rs = MyApp::DB::Album->search({
artist => { '!=', 'Janis Joplin' },
year => { '<' => 1980 },
albumid => [ 1, 14, 15, 65, 43 ]
});
This results in something like the following C<WHERE> clause:
WHERE artist != 'Janis Joplin'
AND year < 1980
AND albumid IN (1, 14, 15, 65, 43)
For more examples of complex queries, see
L<DBIx::Class::Manual::Cookbook>.
The search can also be modified by passing another hash with
attributes:
my @albums = MyApp::DB::Album->search(
{ artist => 'Bob Marley' },
{ rows => 2, order_by => 'year DESC' }
);
C<@albums> then holds the two most recent Bob Marley albums.
For a complete overview of the available attributes, see
L<DBIx::Class::ResultSet/ATTRIBUTES>.
=head1 SEE ALSO
=over 4
=item * L<DBIx::Class::Manual::Cookbook>
=item * L<DBIx::Class::Manual::FAQ>
=back
=cut