3 DBIx::Class::Manual::Intro - Introduction to DBIx::Class
7 You're bored with SQL, and want a native Perl interface for your database? Or
8 you've been doing this for a while with L<Class::DBI>, and think there's a
9 better way? You've come to the right place.
11 =head1 THE DBIx::Class WAY
13 Here are a few simple tips that will help you get your bearings with
16 =head2 Tables become Result classes
18 DBIx::Class needs to know what your Table structure looks like. You
19 do that by defining Result classes. Result classes are defined by
20 calling methods proxied to L<DBIx::Class::ResultSource>. Each Result
21 class defines one Table, which defines the Columns it has, along with
22 any Relationships it has to other tables. (And oh, so much more
23 besides) The important thing to understand:
25 A Result class == Table
27 (most of the time, but just bear with my simplification)
29 =head2 It's all about the ResultSet
31 So, we've got some ResultSources defined. Now, we want to actually use those
32 definitions to help us translate the queries we need into handy perl objects!
34 Let's say we defined a ResultSource for an "album" table with three columns:
35 "albumid", "artist", and "title". Any time we want to query this table, we'll
36 be creating a L<DBIx::Class::ResultSet> from its ResultSource. For example, the
39 SELECT albumid, artist, title FROM album;
41 Would be retrieved by creating a ResultSet object from the album table's
42 ResultSource, likely by using the "search" method.
44 DBIx::Class doesn't limit you to creating only simple ResultSets -- if you
45 wanted to do something like:
47 SELECT title FROM album GROUP BY title;
49 You could easily achieve it.
51 The important thing to understand:
53 Any time you would reach for a SQL query in DBI, you are
54 creating a DBIx::Class::ResultSet.
56 =head2 Search is like "prepare"
58 DBIx::Class tends to wait until it absolutely must fetch information from the
59 database. If you are returning a ResultSet, the query won't execute until you
60 use a method that wants to access the data. (Such as "next", or "first")
62 The important thing to understand:
64 Setting up a ResultSet does not execute the query; retrieving
67 =head2 Search results are returned as Rows
69 Rows of the search from the database are blessed into
70 L<DBIx::Class::Row> objects.
72 =head1 SETTING UP DBIx::Class
74 Let's look at how you can set and use your first native L<DBIx::Class> tree.
76 First we'll see how you can set up your classes yourself. If you want them to
77 be auto-discovered, just skip to the next section, which shows you how to use
78 L<DBIx::Class::Schema::Loader>.
80 =head2 Setting it up manually
82 First, you should create your base schema class, which inherits from
83 L<DBIx::Class::Schema>:
86 use base qw/DBIx::Class::Schema/;
88 In this class you load your result_source ("table", "model") classes, which we
89 will define later, using the load_namespaces() method:
91 # load My::Schema::Result::* and their resultset classes
92 __PACKAGE__->load_namespaces();
94 By default this loads all the Result (Row) classes in the
95 My::Schema::Result:: namespace, and also any resultset classes in the
96 My::Schema::ResultSet:: namespace (if missing, the resultsets are
97 defaulted to be DBIx::Class::ResultSet objects). You can change the
98 result and resultset namespaces by using options to the
99 L<DBIx::Class::Schema/load_namespaces> call.
101 It is also possible to do the same things manually by calling
102 C<load_classes> for the Row classes and defining in those classes any
103 required resultset classes.
105 Next, create each of the classes you want to load as specified above:
107 package My::Schema::Result::Album;
108 use base qw/DBIx::Class/;
110 Load any components required by each class with the load_components() method.
111 This should consist of "Core" plus any additional components you want to use.
112 For example, if you want to force columns to use UTF-8 encoding:
114 __PACKAGE__->load_components(qw/ ForceUTF8 Core /);
116 Set the table for your class:
118 __PACKAGE__->table('album');
120 Add columns to your class:
122 __PACKAGE__->add_columns(qw/ albumid artist title /);
124 Each column can also be set up with its own accessor, data_type and other pieces
125 of information that it may be useful to have -- just pass C<add_columns> a hash:
127 __PACKAGE__->add_columns(albumid =>
128 { accessor => 'album',
129 data_type => 'integer',
132 is_auto_increment => 1,
136 { data_type => 'integer',
139 is_auto_increment => 0,
143 { data_type => 'varchar',
146 is_auto_increment => 0,
151 DBIx::Class doesn't directly use most of this data yet, but various related
152 modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you to
153 create your database tables from your Schema, instead of the other way around.
154 See L<SQL::Translator> for details.
156 See L<DBIx::Class::ResultSource> for more details of the possible column
159 Accessors are created for each column automatically, so My::Schema::Result::Album will
160 have albumid() (or album(), when using the accessor), artist() and title()
163 Define a primary key for your class:
165 __PACKAGE__->set_primary_key('albumid');
167 If you have a multi-column primary key, just pass a list instead:
169 __PACKAGE__->set_primary_key( qw/ albumid artistid / );
171 Define this class' relationships with other classes using either C<belongs_to>
172 to describe a column which contains an ID of another Table, or C<has_many> to
173 make a predefined accessor for fetching objects that contain this Table's
176 __PACKAGE__->has_many('albums', 'My::Schema::Result::Artist', 'album_id');
178 See L<DBIx::Class::Relationship> for more information about the various types of
179 available relationships and how you can design your own.
181 =head2 Using L<DBIx::Class::Schema::Loader>
183 This is an external module, and not part of the L<DBIx::Class> distribution.
184 Like L<Class::DBI::Loader>, it inspects your database, and automatically creates
185 classes for all the tables in your database. Here's a simple setup:
188 use base qw/DBIx::Class::Schema::Loader/;
190 __PACKAGE__->loader_options( relationships => 1 );
194 The actual autoloading process will occur when you create a connected instance
195 of your schema below.
197 See the L<DBIx::Class::Schema::Loader> documentation for more information on its
202 To connect to your Schema, you need to provide the connection details. The
203 arguments are the same as for L<DBI/connect>:
205 my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
207 You can create as many different schema instances as you need. So if you have a
208 second database you want to access:
210 my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs );
212 Note that L<DBIx::Class::Schema> does not cache connections for you. If you use
213 multiple connections, you need to do this manually.
215 To execute some sql statements on every connect you can add them as an option in
216 a special fifth argument to connect:
218 my $another_schema = My::Schema->connect(
223 { on_connect_do => \@on_connect_sql_statments }
226 See L<DBIx::Class::Schema::Storage::DBI/connect_info> for more information about
227 this and other special C<connect>-time options.
231 Once you've defined the basic classes, either manually or using
232 L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
234 To access your database using your $schema object, you can fetch a
235 L<DBIx::Class::Manual::Glossary/"ResultSet"> representing each of your tables by
236 calling the C<resultset> method.
238 The simplest way to get a record is by primary key:
240 my $album = $schema->resultset('Album')->find(14);
242 This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause, and
243 return an instance of C<My::Schema::Result::Album> that represents this row. Once you
244 have that row, you can access and update columns:
246 $album->title('Physical Graffiti');
247 my $title = $album->title; # $title holds 'Physical Graffiti'
249 If you prefer, you can use the C<set_column> and C<get_column> accessors
252 $album->set_column('title', 'Presence');
253 $title = $album->get_column('title');
255 Just like with L<Class::DBI>, you call C<update> to commit your changes to the
260 If needed, you can throw away your local changes:
262 $album->discard_changes if $album->is_changed;
264 As you can see, C<is_changed> allows you to check if there are local changes to
267 =head2 Adding and removing rows
269 To create a new record in the database, you can use the C<create> method. It
270 returns an instance of C<My::Schema::Result::Album> that can be used to access the data
273 my $new_album = $schema->resultset('Album')->create({
274 title => 'Wish You Were Here',
275 artist => 'Pink Floyd'
278 Now you can add data to the new record:
280 $new_album->label('Capitol');
281 $new_album->year('1975');
284 Likewise, you can remove it from the database:
288 You can also remove records without retrieving them first, by calling delete
289 directly on a ResultSet object.
291 # Delete all of Falco's albums
292 $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
294 =head2 Finding your objects
296 L<DBIx::Class> provides a few different ways to retrieve data from your
297 database. Here's one example:
299 # Find all of Santana's albums
300 my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
302 In scalar context, as above, C<search> returns a L<DBIx::Class::ResultSet>
303 object. It can be used to peek at the first album returned by the database:
305 my $album = $rs->first;
308 You can loop over the albums and update each one:
310 while (my $album = $rs->next) {
311 print $album->artist . ' - ' . $album->title;
316 Or, you can update them all at once:
318 $rs->update({ year => 2001 });
320 In list context, the C<search> method returns all of the matching rows:
322 # Fetch immediately all of Carlos Santana's albums
323 my @albums = $schema->resultset('Album')->search(
324 { artist => 'Carlos Santana' }
326 foreach my $album (@albums) {
327 print $album->artist . ' - ' . $album->title;
330 We also provide a handy shortcut for doing a C<LIKE> search:
332 # Find albums whose artist starts with 'Jimi'
333 my $rs = $schema->resultset('Album')->search_like({ artist => 'Jimi%' });
335 Or you can provide your own C<WHERE> clause:
337 # Find Peter Frampton albums from the year 1986
338 my $where = 'artist = ? AND year = ?';
339 my @bind = ( 'Peter Frampton', 1986 );
340 my $rs = $schema->resultset('Album')->search_literal( $where, @bind );
342 The preferred way to generate complex queries is to provide a L<SQL::Abstract>
343 construct to C<search>:
345 my $rs = $schema->resultset('Album')->search({
346 artist => { '!=', 'Janis Joplin' },
347 year => { '<' => 1980 },
348 albumid => { '-in' => [ 1, 14, 15, 65, 43 ] }
351 This results in something like the following C<WHERE> clause:
353 WHERE artist != 'Janis Joplin'
355 AND albumid IN (1, 14, 15, 65, 43)
357 For more examples of complex queries, see L<DBIx::Class::Manual::Cookbook>.
359 The search can also be modified by passing another hash with
362 my @albums = My::Schema->resultset('Album')->search(
363 { artist => 'Bob Marley' },
364 { rows => 2, order_by => 'year DESC' }
367 C<@albums> then holds the two most recent Bob Marley albums.
369 For more information on what you can do with a L<DBIx::Class::ResultSet>, see
370 L<DBIx::Class::ResultSet/METHODS>.
372 For a complete overview of the available attributes, see
373 L<DBIx::Class::ResultSet/ATTRIBUTES>.
377 =head2 Problems on RHEL5/CentOS5
379 There used to be an issue with the system perl on Red Hat Enterprise
380 Linux 5, some versions of Fedora and derived systems. Further
381 information on this can be found in L<DBIx::Class::Manual::Troubleshooting>
387 =item * L<DBIx::Class::Manual::Cookbook>