=head2 SELECT DISTINCT with multiple columns
- my $rs = $schema->resultset('Foo')->search(
+ my $rs = $schema->resultset('Artist')->search(
{},
{
- select => [
- { distinct => [ $source->columns ] }
- ],
- as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
+ columns => [ qw/artist_id name rank/ ],
+ distinct => 1
+ }
+ );
+
+ my $rs = $schema->resultset('Artist')->search(
+ {},
+ {
+ columns => [ qw/artist_id name rank/ ],
+ group_by => [ qw/artist_id name rank/ ],
}
);
+ # Equivalent SQL:
+ # SELECT me.artist_id, me.name, me.rank
+ # FROM artist me
+ # GROUP BY artist_id, name, rank
+
=head2 SELECT COUNT(DISTINCT colname)
- my $rs = $schema->resultset('Foo')->search(
+ my $rs = $schema->resultset('Artist')->search(
{},
{
- select => [
- { count => { distinct => 'colname' } }
- ],
- as => [ 'count' ]
+ columns => [ qw/name/ ],
+ distinct => 1
}
);
- my $count = $rs->next->get_column('count');
+ my $rs = $schema->resultset('Artist')->search(
+ {},
+ {
+ columns => [ qw/name/ ],
+ group_by => [ qw/name/ ],
+ }
+ );
+
+ my $count = $rs->count;
+
+ # Equivalent SQL:
+ # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
=head2 Grouping results
my $rs = $cdrs->search({
year => {
'=' => $cdrs->search(
- { artistid => { '=' => \'me.artistid' } },
+ { artist_id => { '=' => \'me.artist_id' } },
{ alias => 'inner' }
)->get_column('year')->max_rs->as_query,
},
WHERE year = (
SELECT MAX(inner.year)
FROM cd inner
- WHERE artistid = me.artistid
+ WHERE artist_id = me.artist_id
)
=head3 EXPERIMENTAL
=head2 Using joins and prefetch
You can use the C<join> attribute to allow searching on, or sorting your
-results by, one or more columns in a related table. To return all CDs matching
-a particular artist name:
+results by, one or more columns in a related table.
+
+This requires that you have defined the L<DBIx::Class::Relationship>. For example :
+
+ My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
+
+To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist', # join the artist table
+ join => 'artists', # join the artist table
}
);
# JOIN artist ON cd.artist = artist.id
# WHERE artist.name = 'Bob Marley'
+In that example both the join, and the condition use the relationship name rather than the table name
+(see DBIx::Class::Manual::Joining for more details on aliasing ).
+
If required, you can now sort on any column in the related tables by including
-it in your C<order_by> attribute:
+it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist',
- order_by => [qw/ artist.name /]
+ join => 'artists',
+ order_by => [qw/ artists.name /]
}
);
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist',
- order_by => [qw/ artist.name /],
- prefetch => 'artist' # return artist data too!
+ join => 'artists',
+ order_by => [qw/ artists.name /],
+ prefetch => 'artists' # return artist data too!
}
);
so no additional SQL statements are executed. You now have a much more
efficient query.
-Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
-C<has_many> relationships.
-
Also note that C<prefetch> should only be used when you know you will
definitely use data from a related table. Pre-fetching related tables when you
only need columns from the main table will make performance worse!
=head2 Multi-step prefetch
-From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
+C<prefetch> can be nested more than one relationship
deep using the same syntax as a multi-step join:
my $rs = $schema->resultset('Tag')->search(
AKA getting last_insert_id
-If you are using PK::Auto (which is a core component as of 0.07), this is
-straightforward:
+Thanks to the core component PK::Auto, this is straightforward:
my $foo = $rs->create(\%blah);
# do more stuff
# do whatever else you wanted if it was a new row
}
+=head2 Static sub-classing DBIx::Class result classes
+
+AKA adding additional relationships/methods/etc. to a model for a
+specific usage of the (shared) model.
+
+B<Schema definition>
+
+ package My::App::Schema;
+
+ use base DBIx::Class::Schema;
+
+ # load subclassed classes from My::App::Schema::Result/ResultSet
+ __PACKAGE__->load_namespaces;
+
+ # load classes from shared model
+ load_classes({
+ 'My::Shared::Model::Result' => [qw/
+ Foo
+ Bar
+ /]});
+
+ 1;
+
+B<Result-Subclass definition>
+
+ package My::App::Schema::Result::Baz;
+
+ use strict;
+ use warnings;
+ use base My::Shared::Model::Result::Baz;
+
+ # WARNING: Make sure you call table() again in your subclass,
+ # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
+ # and the class name is not correctly registered as a source
+ __PACKAGE__->table('baz');
+
+ sub additional_method {
+ return "I'm an additional method only needed by this app";
+ }
+
+ 1;
+
=head2 Dynamic Sub-classing DBIx::Class proxy classes
AKA multi-class object inflation from one table
use base qw/DBIx::Class::Schema/;
- __PACKAGE__->load_namespaces;
+ __PACKAGE__->load_namespaces;
+
+ 1;
B<Proxy-Class definitions>
print "I am a regular user.\n";
return ;
}
-
+
+ 1;
+
package My::Schema::Result::User::Admin;
{
print "I am doing admin stuff\n";
return ;
- }
+ }
+
+ 1;
B<Test File> test.pl
__PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
- __PACKAGE__->add_columns(qw/ artistid name /);
- __PACKAGE__->set_primary_key('artistid');
+ __PACKAGE__->add_columns(qw/ artist_id name /);
+ __PACKAGE__->set_primary_key('artist_id');
__PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1;
projects / dbsrgits/DBIx-Class-Historic.git / blobdiff