Sometimes you need to formulate a query using specific operators:
- my @albums = MyApp::DB::Album->search({
- artist => { 'like', '%Lamb%' },
- title => { 'like', '%Fear of Fours%' },
- });
+ my @albums = MyApp::DB::Album->search({
+ artist => { 'like', '%Lamb%' },
+ title => { 'like', '%Fear of Fours%' },
+ });
This results in something like the following C<WHERE> clause:
- WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
+ WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
Other queries might require slightly more complex logic:
- my @albums = MyApp::DB::Album->search({
- -or => [
- -and => [
- artist => { 'like', '%Smashing Pumpkins%' },
- title => 'Siamese Dream',
- ],
- artist => 'Starchildren',
- ],
- });
+ my @albums = MyApp::DB::Album->search({
+ -or => [
+ -and => [
+ artist => { 'like', '%Smashing Pumpkins%' },
+ title => 'Siamese Dream',
+ ],
+ artist => 'Starchildren',
+ ],
+ });
This results in the following C<WHERE> clause:
- WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
- OR artist = 'Starchildren'
+ WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
+ OR artist = 'Starchildren'
For more information on generating complex queries, see
L<SQL::Abstract/WHERE CLAUSES>.
development, you might like to put the following signal handler in
your main database class to make sure it disconnects cleanly:
- $SIG{INT} = sub {
- __PACKAGE__->storage->dbh->disconnect;
- };
+ $SIG{INT} = sub {
+ __PACKAGE__->storage->dbh->disconnect;
+ };
=head2 Using joins and prefetch
=head2 Transactions
As of version 0.04001, there is improved transaction support in
-L<DBIx::Class::Storage::DBI>. Here is an example of the recommended
+L<DBIx::Class::Storage::DBI>. Here is an example of the recommended
way to use it:
- my $genus = Genus->find(12);
+ my $genus = Genus->find(12);
+ eval {
+ MyDB->txn_begin;
+ $genus->add_to_species({ name => 'troglodyte' });
+ $genus->wings(2);
+ $genus->update;
+ cromulate($genus); # Can have a nested transation
+ MyDB->txn_commit;
+ };
+ if ($@) {
+ # Rollback might fail, too
eval {
- MyDB->txn_begin;
- $genus->add_to_species({ name => 'troglodyte' });
- $genus->wings(2);
- $genus->update;
- cromulate($genus); # Can have a nested transation
- MyDB->txn_commit;
+ MyDB->txn_rollback
};
- if ($@) {
- # Rollback might fail, too
- eval {
- MyDB->txn_rollback
- };
- }
+ }
Currently, a nested commit will do nothing and a nested rollback will
-die. The code at each level must be sure to call rollback in the case
+die. The code at each level must be sure to call rollback in the case
of an error, to ensure that the rollback will propagate to the top
-level and be issued. Support for savepoints and for true nested
+level and be issued. Support for savepoints and for true nested
transactions (for databases that support them) will hopefully be added
in the future.
=head2 Many-to-many relationships
-This is not as easy as it could be, but it's possible. Here's an
+This is not as easy as it could be, but it's possible. Here's an
example to illustrate:
- # Set up inherited connection information
- package MyApp::DBIC;
- use base qw/DBIx::Class/;
-
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
- __PACKAGE__->connection(...);
-
- # Set up a class for the 'authors' table
- package MyApp::DBIC::Author;
- use base qw/MyApp::DBIC/;
-
- __PACKAGE__->table('authors');
- __PACKAGE__->add_columns(qw/authID first_name last_name/);
- __PACKAGE__->set_primary_key(qw/authID/);
-
- # Define relationship to the link table
- __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'authID');
-
- # Create the accessor for books from the Author class
- sub books {
- my ($self) = @_;
- return MyApp::DBIC::Book->search(
- { 'b2a.authID' => $self->authID }, # WHERE clause
- { join => 'b2a' } # join condition (part of search attrs)
- # 'b2a' refers to the relationship named earlier in the Author class.
- # 'b2a.authID' refers to the authID column of the b2a relationship,
- # which becomes accessible in the search by being joined.
- );
- }
-
- # Define the link table class
- package MyApp::DBIC::Book2Author;
- use base qw/MyApp::DBIC/;
-
- __PACKAGE__->table('book2author');
- __PACKAGE__->add_columns(qw/bookID authID/);
- __PACKAGE__->set_primary_key(qw/bookID authID/);
-
- __PACKAGE__->belongs_to('authID' => 'MyApp::DBIC::Author');
- __PACKAGE__->belongs_to('bookID' => 'MyApp::DBIC::Book');
-
- package MyApp::DBIC::Book;
- use base qw/MyApp::DBIC/;
-
- __PACKAGE__->table('books');
- __PACKAGE__->add_columns(qw/bookID title edition isbn publisher year/);
- __PACKAGE__->set_primary_key(qw/bookID/);
-
- __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'bookID');
-
-
- # Returns an author record where the bookID field of the
- # book2author table equals the bookID of the books (using the
- # bookID relationship table)
- sub authors {
- my ($self) = @_;
- return MyApp::DBIC::Author->search(
- { 'b2a.bookID' => $self->bookID }, # WHERE clause
- { join => 'b2a' } # JOIN condition
- );
- }
+ # Set up inherited connection information
+ package MyApp::DBIC;
+ use base qw/DBIx::Class/;
+
+ __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+ __PACKAGE__->connection(...);
+
+ # Set up a class for the 'authors' table
+ package MyApp::DBIC::Author;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('authors');
+ __PACKAGE__->add_columns(qw/authID first_name last_name/);
+ __PACKAGE__->set_primary_key(qw/authID/);
+
+ # Define relationship to the link table
+ __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'authID');
+
+ # Create the accessor for books from the Author class
+ sub books {
+ my ($self) = @_;
+ return MyApp::DBIC::Book->search(
+ { 'b2a.authID' => $self->authID }, # WHERE clause
+ { join => 'b2a' } # join condition (part of search attrs)
+ # 'b2a' refers to the relationship named earlier in the Author class.
+ # 'b2a.authID' refers to the authID column of the b2a relationship,
+ # which becomes accessible in the search by being joined.
+ );
+ }
+
+ # Define the link table class
+ package MyApp::DBIC::Book2Author;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('book2author');
+ __PACKAGE__->add_columns(qw/bookID authID/);
+ __PACKAGE__->set_primary_key(qw/bookID authID/);
+
+ __PACKAGE__->belongs_to('authID' => 'MyApp::DBIC::Author');
+ __PACKAGE__->belongs_to('bookID' => 'MyApp::DBIC::Book');
+
+ package MyApp::DBIC::Book;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('books');
+ __PACKAGE__->add_columns(qw/bookID title edition isbn publisher year/);
+ __PACKAGE__->set_primary_key(qw/bookID/);
+
+ __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'bookID');
+
+
+ # Returns an author record where the bookID field of the
+ # book2author table equals the bookID of the books (using the
+ # bookID relationship table)
+ sub authors {
+ my ($self) = @_;
+ return MyApp::DBIC::Author->search(
+ { 'b2a.bookID' => $self->bookID }, # WHERE clause
+ { join => 'b2a' } # JOIN condition
+ );
+ }
=head2 Setting default values
-It's as simple as overriding the C<new> method. Note the use of
+It's as simple as overriding the C<new> method. Note the use of
C<next::method>.
- sub new {
- my ( $class, $attrs ) = @_;
+ sub new {
+ my ( $class, $attrs ) = @_;
- $attrs->{foo} = 'bar' unless defined $attrs->{foo};
+ $attrs->{foo} = 'bar' unless defined $attrs->{foo};
- $class->next::method($attrs);
- }
+ $class->next::method($attrs);
+ }
=head2 Stringification
Employ the standard stringification technique by using the C<overload>
-module. Replace C<foo> with the column/method of your choice.
+module. Replace C<foo> with the column/method of your choice.
- use overload '""' => 'foo', fallback => 1;
+ use overload '""' => 'foo', fallback => 1;
=cut
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.
+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
+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 DBIx::Class
-like this:
+First, you'll need a base class. It should inherit from
+L<DBIx::Class> like this:
- package MyApp::DB;
- use base qw/DBIx::Class/;
+ package MyApp::DB;
+ 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 C<DB> in this introduction, since it involves less magic.
-L<Schema> is mostly useful if you want to use multiple database
+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/);
+ __PACKAGE__->load_components(qw/Core DB/);
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example. The
-L<DBIx::Class::PK::Auto> modules help L<DBIx::Class> keep up with
-newly generated keys in auto increment database fields.
+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/);
+ __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
-Once you've loaded the components, it's time to set up your connection:
+C<PK::Auto> classes exist for many databases; see
+L<DBIx::Class::PK::Auto> for more information.
- __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+Once you've loaded the components, it's time to set up your
+connection:
-This method is similar to the normal L<DBI>, and can take username,
-password, and L<DBI> attribute hash as well as the DSN.
+ __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/;
+ package MyApp::DB::Album;
+ use base qw/MyApp::DB/;
Then we specify which table it uses,
- __PACKAGE__->table('album');
+ __PACKAGE__->table('album');
and specify which columns it has.
- __PACKAGE__->add_columns(qw/albumID artist title label year/);
+ __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');
+ __PACKAGE__->set_primary_key('albumid');
-If you have multiple primary keys, just pass a list instead.
+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
+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>.
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:
+and automatically creates classes for all the tables in your database.
+Here's a simple setup:
- package MyApp::DB;
- use DBIx::Class::Loader;
+ package MyApp::DB;
+ use DBIx::Class::Loader;
- my $loader = DBIx::Class::Loader->new(
- dsn => 'dbi:SQLite:/home/me/myapp/my.db',
- namespace => 'MyApp::DB'
- );
+ my $loader = DBIx::Class::Loader->new(
+ dsn => 'dbi:SQLite:/home/me/myapp/my.db',
+ namespace => 'MyApp::DB'
+ );
- 1;
+ 1;
-This should be equivalent to the manual in the section above.
-L<DBIx::Class::Loader> takes lots of other options. For more
+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, you can start interacting with
-your database. The simplest way to get a column is by primary key:
+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 $albumID = 14;
- my $album = MyApp::DB::Album->find($albumID);
+ my $album = MyApp::DB::Album->find(14);
-This will run a select with C<albumID = 14> in the C<WHERE> clause,
-and return an instance of C<MyApp::DB::Artist> that represents this
-row. Once you have that row, you can access and update columns:
+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'
+ $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');
+ $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;
+ $album->update;
-If needed, you can drop your local changes instead like this:
+If needed, you can throw away your local changes like this:
- $album->discard_changes if $album->is_changed;
+ $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 from L<DBIx::Class::Row>. It returns a
-L<DBIx::Class::ResultSet> object that can be used to access the data
-in the new record.
+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'
- });
+ 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->label('Capitol');
+ $new_album->year('1975');
+ $new_album->update;
-Likewise, you can remove if from the database like this:
+Likewise, you can remove it from the database like this:
- $new_album->delete;
+ $new_album->delete;
-or even without retrieving first. This operation takes the same kind
-of arguments as a search.
+You can also remove records without or retrieving first. This
+operation takes the same kind of arguments as a search.
- MyApp::DB::Album->delete({ artist => 'Falco' });
+ # 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. The simplest looks something like this:
+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;
- my $iter = MyApp::DB::Album->search( artist => 'Santana' );
+Or, you can loop over the albums and update each one:
-Note that all the C<search> methods return a L<DBIx::Class::ResultSet>
-object in scalar context. So, if you want the first album:
+ while (my $album = $rs->next) {
+ print $album->artist . ' - ' . $album->title;
+ $album->year(2001);
+ $album->update;
+ }
- my $album = $iter->first;
+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> methods return all of the matching
+In list context, the C<search> method returns all of the matching
rows:
- my @albums = MyApp::DB::Album->search( artist => 'Santana' );
+ # 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:
- my $iter = MyApp::DB::Album->search_like( artist => 'Jimi%' );
+ # 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:
-
- my $iter = MyApp::DB::Album->search_literal( 'artist = ?', 'Peter Frampton' );
+
+ # 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 $iter = MyApp::DB::Album->search({
- artist => { '!=', 'Janis Joplin' },
- year => { '<' => 1980 },
- id => [ 1, 14, 15, 65, 43 ]
- });
+ 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:
-For more examples of complex searches, see
+ 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 $iter = MyApp::DB::Album->search(
- { artist => 'Bob Marley' },
- { page => 1, rows => 2, order_by => 'year' }
- );
+ 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>.
projects / dbsrgits/DBIx-Class.git / commitdiff