=head1 NAME
-DBIx::Class::Manual::Intro
+DBIx::Class::Manual::Intro - Introduction to DBIx::Class
-=head1 Introduction.
+=head1 INTRODUCTION
-So, you are bored with SQL, and want a native perl interface for your classes?
-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 DBIx::Class tree.
+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.
-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 DBIx::Class::Loader.
+=head1 THE DBIx::Class WAY
+
+Here are a few simple tips that will help you get your bearings
+with DBIx::Class.
+
+=head2 Tables become ResultSources
+
+DBIx::Class needs to know what your Table structure looks like. You do that
+by defining L<DBIx::Class::ResultSource>s. Each table get's a ResultSource,
+which defines the Columns it has, along with any Relationships it has to
+other tables. (And oh, so much more besides) The important thing to
+understand:
+
+ A ResultSource == Table
+
+(most of the time, but just bear with my simplification)
+
+=head2 It's all about the ResultSet
+
+So, we've got some ResultSources defined. Now, we want to actually use
+those definitions to help us translate the queries we need into
+handy perl objects!
+
+Let's say we defined a ResultSource for an "album" table with three
+columns: "albumid", "artist", and "title". Any time we want to query
+this table, we'll be creating a L<DBIx::Class::ResultSet> from it's
+ResultSource. For example, the results of:
+
+ SELECT albumid, artist, title FROM album;
+
+Would be retrieved by creating a ResultSet object from the album
+table's ResultSource, likely by using the "search" method.
+
+DBIx::Class doesn't limit you to creating only simple ResultSets --
+if you wanted to do something like:
+
+ SELECT title FROM album GROUP BY title;
+
+You could easily achieve it.
+
+The important thing to understand:
+
+ Any time you would reach for a SQL query in DBI, you are
+ creating a DBIx::Class::ResultSet.
+
+=head2 Search is like "prepare"
+
+DBIx::Class tends to wait until it absolutely must fetch information
+from the database. If you are returning a ResultSet, the query won't
+execute until you use a method that wants to access the data. (Such
+as "next", or "first")
+
+The important thing to understand:
+
+ Setting up a ResultSet does not execute the query; retrieving
+ the data does.
+
+=head1 SETTING UP DBIx::Class
+
+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::Schema::Loader>.
=head2 Setting it up manually
-First, you'll need a base class. It should inherit from DBIx::Class
-like this:
+First, you should create your base schema class, which inherits from
+L<DBIx::Class::Schema>:
+
+ package My::Schema;
+ use base qw/DBIx::Class::Schema/;
+
+In this class you load your result_source ("table", "model") classes, which
+we will define later, using the load_classes() method. You can specify which
+classes to load manually:
+
+ # load My::Schema::Album and My::Schema::Artist
+ __PACKAGE__->load_classes(qw/ Album Artist /);
+
+Or load classes by namespace:
- package MyApp::DB
+ # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes
+ __PACKAGE__->load_classes(
+ {
+ 'My::Schema' => [qw/ Album Artist /],
+ 'My::OtherSchema' => [qw/ LinerNotes /]
+ }
+ );
+
+Or let your schema class load all classes in its namespace automatically:
+
+ # load My::Schema::*
+ __PACKAGE__->load_classes();
+
+Next, create each of the classes you want to load as specified above:
+
+ package My::Schema::Album;
use base qw/DBIx::Class/;
-You will also want to load some of L<DBIx::Class>'s components.
-L<DBIx::Class::Core> provides a good basic set. In addition you'll
-have to use either L<DBIx::Class::Schema> or L<DBIx::Class::DB> We'll
-use DB in this introduction, since it involves less magic. Schema is
-mostly useful if you want to use multiple database connections.
+Load any components required by each class with the load_components() method.
+This should consist of "Core" plus any additional components you want to use.
+For example, if you want serial/auto-incrementing primary keys:
- __PACKAGE__->load_components(qw/Core DB/);
+ __PACKAGE__->load_components(qw/ PK::Auto Core /);
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example
+C<PK::Auto> is supported for many databases; see
+L<DBIx::Class::Storage::DBI> for more information.
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+Set the table for your class:
-Once you've loaded the components, it's time to set up your connection:
+ __PACKAGE__->table('album');
- __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+Add columns to your class:
-This method is similar to the normal L<DBI>, and can take user/pass/dbi
-attribute hash as well as the dsn.
+ __PACKAGE__->add_columns(qw/ albumid artist title /);
-With that out of the way, we can define our first table class:
+Each column can also be set up with its own accessor, data_type and other
+pieces of information that it may be useful to have, just pass C<add_columns>
+a hash such as:
- package MyApp::DB::Frob
+ __PACKAGE__->add_columns(albumid =>
+ { accessor => 'album',
+ data_type => 'integer',
+ size => 16,
+ is_nullable => 0,
+ is_auto_increment => 1,
+ default_value => '',
+ },
+ artist =>
+ { data_type => 'integer',
+ size => 16,
+ is_nullable => 0,
+ is_auto_increment => 0,
+ default_value => '',
+ },
+ title =>
+ { data_type => 'varchar',
+ size => 256,
+ is_nullable => 0,
+ is_auto_increment => 0,
+ default_value => '',
+ }
+ );
- use base qw/MyApp::DB/;
+Most of this data isn't yet used directly by DBIx::Class, but various related
+modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you
+to create your database tables from your Schema, instead of the other way
+around. See L<SQL::Translator> for details.
-Then we specify which table it uses,
+See L<DBIx::Class::ResultSource> for more details of the possible column
+attributes.
- __PACKAGE__->table('frob');
+Accessors are created for each column automatically, so My::Schema::Album will
+have albumid() (or album(), when using the accessor), artist() and title()
+methods.
-and specify which columns it has.
+Define a primary key for your class:
- __PACKAGE__->add_columns(qw/id foo bar/);
+ __PACKAGE__->set_primary_key('albumid');
-This will automatically create accessors for each of the columns, so that
-you can read/update the values in rows you've retrieved.
+If you have a multi-column primary key, just pass a list instead:
-Also, you need to tell it which column is the primary key:
+ __PACKAGE__->set_primary_key( qw/ albumid artistid / );
- __PACKAGE__->set_primary_key('id');
+Define relationships that the class has with any other classes by using
+either C<belongs_to> to describe a column which contains an ID of another
+table, or C<has_many> to make a predefined accessor for fetching objects
+that contain this tables foreign key in one of their columns:
-If you have multiple primary keys, just pass a list instead.
+ __PACKAGE__->has_many('albums', 'My::Schema::Artist', 'album_id');
-That's pretty much all you need for a basic setup. If you have more advanced
-needs like using more than 1 database connections for the same class, see
-L<DBIx::Class::Schema>.
+More information about the various types of relationships available, and
+how you can design your own, can be found in L<DBIx::Class::Relationship>.
-=head2 Using L<DBIx::Class::Loader>.
+=head2 Using L<DBIx::Class::Schema::Loader>
-This is an additional class, and not part of the 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:
+This is an external module, 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;
+ package My::Schema;
+ use base qw/DBIx::Class::Schema::Loader/;
+
+ __PACKAGE__->loader_options( relationships => 1 );
- 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 in the section above.
-L<DBIx::Class::Loader> takes lots of other options. For more information,
-consult the reference documentation.
+The actual autoloading process will occur when you create a connected
+instance of your schema below.
-=head2 Basic Usage
+L<DBIx::Class::Schema::Loader> takes lots of other options. For more
+information, consult its documentation.
-Once you've defined the basic classes, you can start interacting with your
-database. The simplest way to get a column is by primary key:
+=head2 Connecting
- my $frob=MyApp::DB::Frob->find(14);
+To connect to your Schema, you also need to provide the connection details.
+The arguments are the same as you would use for L<DBI/connect>:
-This will run a select with id=14 in the WHERE clause, and return an instance
-of MyApp::DB::Frob that represents this row. Once you have that row, you can
-access and update columns
+ my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
- my $val=$frob->bar;
- $frob->bar(14);
+You can create as many different schema instances as you need. So if you have
+a second database you want to access:
-or if you prefer, you can use the set_column/get_column accessors instead
-of the autogenerated accessors based on your column names.
+ my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs );
-Just like with L<Class::DBI>, you do an 'update' to commit your changes
-to the database:
+Note that L<DBIx::Class::Schema> does not cache connections for you. If you
+use multiple connections, you need to do this manually.
- $frob->update;
+To execute some sql statements on every connect you can add them as an option
+in a special fifth argument to connect, like so:
-If needed, you can drop your local changes instead like this:
+ my $another_schema = My::Schema->connect(
+ $dsn,
+ $user,
+ $password,
+ $attrs,
+ { on_connect_do => \@on_connect_sql_statments }
+ );
- $frob->discard_changes if $frob->is_changed;
+For more information about this and other special C<connect()>-time options,
+see L<DBIx::Class::Schema::Storage::DBI/connect_info>.
-As you can see, is_changed allows you to check if there are local changes to
-your object.
+=head2 Basic usage
-=head2 Adding and removing rows.
+Once you've defined the basic classes, either manually or using
+L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
-To make a new row, and put it into the database, you can use the 'create'
-method from L<DBIx::Class::Row>
+To access your database using your $schema object, you can fetch a L<DBIx::Class::Manual::Glossary/"ResultSet">
+representing each of your tables by calling the ->resultset method.
- my $new_thingie=MyApp::DB::Frob->create({
- foo=>'homer',
- bar=>'bart' });
+The simplest way to get a record is by primary key:
-likewise, you can remove if from the database like this:
+ my $album = $schema->resultset('Album')->find(14);
- $new_thingie->delete();
+This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause,
+and return an instance of C<My::Schema::Album> that represents this
+row. Once you have that row, you can access and update columns:
-or even without retrieving first. This operation takes the same kind of
-arguments as a search.
+ $album->title('Physical Graffiti');
+ my $title = $album->title; # $title holds 'Physical Graffiti'
- MyApp::DB::Frob->delete({foo=>'bart'});
+If you prefer, you can use the C<set_column> and C<get_column>
+accessors instead:
-=head2 Finding your objects.
+ $album->set_column('title', 'Presence');
+ $title = $album->get_column('title');
-DBIx::Class provides a few different ways to retrieve data from your database.
-The simplest looks something like this:
+Just like with L<Class::DBI>, you call C<update> to commit your
+changes to the database:
- $rs=MyApp::DB::Frob->search(foo=>'bart');
+ $album->update;
-note that all the search methods return a recordset in scalar context or
-a list containing all the elements in list context.
+If needed, you can throw away your local changes like this:
-We also provide a handy shortcut for doing a like search:
+ $album->discard_changes if $album->is_changed;
- $rs=MyApp::DB::Frob->search_like(foo=>'bar%');
+As you can see, C<is_changed> allows you to check if there are local
+changes to your object.
-Or you can provide your own handmade WHERE clause, like
-
- $rs=MyApp::DB::Frob->search_literal('foo=?','bart');
+=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<My::Schema::Album> that can be
+used to access the data in the new record:
-The other way to provide more complex queries, is to provide a
-L<SQL::Abstract> construct to search:
+ my $new_album = $schema->resultset('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 retrieving them first, by calling
+delete directly on a ResultSet object.
+
+ # Delete all of Falco's albums
+ $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
+
+=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 = $schema->resultset('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;
+
+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;
+ }
+
+Or, you can update them all at once:
+
+ $rs->update({ year => 2001 });
- $rs=MyApp::DB::Frob->search({
- bar=>{'>' => 10 },
- foo=>{'!=','bart'},
- id => [1,14,15,65,43]
+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 = $schema->resultset('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 = $schema->resultset('Album')->search_like({ artist => 'Jimi%' });
+
+Or you can provide your own C<WHERE> clause, like:
+
+ # Find Peter Frampton albums from the year 1986
+ my $where = 'artist = ? AND year = ?';
+ my @bind = ( 'Peter Frampton', 1986 );
+ my $rs = $schema->resultset('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 = $schema->resultset('Album')->search({
+ artist => { '!=', 'Janis Joplin' },
+ year => { '<' => 1980 },
+ albumid => { '-in' => [ 1, 14, 15, 65, 43 ] }
});
-The search can also be modifyed by passing another hash with attributes:
+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 = My::Schema->resultset('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
- $rs=MyApp::DB::Frob->search( {foo=>'bart'},
- { page=>1, rows=>2, order_by=>'bar' } );
+=item * L<DBIx::Class::Manual::Cookbook>
-For a complete overview over the available attributes, see
-L<DBIx::Class::ResultSet>
+=back
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff