For more information on generating complex queries, see
L<SQL::Abstract/WHERE CLAUSES>.
+=head2 Retrieve one and only one row from a resultset
+
+Sometimes you need only the first "top" row of a resultset. While this can be
+easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
+as a full blown cursor for the resultset will be created and then immediately
+destroyed after fetching the first row object.
+L<< $rs->single|DBIx::Class::ResultSet/single >> is
+designed specifically for this case - it will grab the first returned result
+without even instantiating a cursor.
+
+Before replacing all your calls to C<first()> with C<single()> please observe the
+following CAVEATS:
+
+=over
+
+=item *
+While single() takes a search condition just like search() does, it does
+_not_ accept search attributes. However one can always chain a single() to
+a search():
+
+ my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
+
+
+=item *
+Since single() is the engine behind find(), it is designed to fetch a
+single row per database query. Thus a warning will be issued when the
+underlying SELECT returns more than one row. Sometimes however this usage
+is valid: i.e. we have an arbitrary number of cd's but only one of them is
+at the top of the charts at any given time. If you know what you are doing,
+you can silence the warning by explicitly limiting the resultset size:
+
+ my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
+
+=back
+
=head2 Arbitrary SQL through a custom ResultSource
Sometimes you have to run arbitrary SQL because your query is too complex
SQL
# Finally, register your new ResultSource with your Schema
- My::Schema->register_source( 'UserFriendsComplex' => $new_source );
+ My::Schema->register_extra_source( 'UserFriendsComplex' => $new_source );
Next, you can execute your complex query using bind parameters like this:
}
) ];
-... and you'll get back a perfect L<DBIx::Class::ResultSet>.
+... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
+that you cannot modify the rows it contains, ie. cannot call L</update>,
+L</delete>, ... on it).
+
+If you prefer to have the definitions of these custom ResultSources in separate
+files (instead of stuffing all of them into the same resultset class), you can
+achieve the same with subclassing the resultset class and defining the
+ResultSource there:
+
+ package My::Schema::UserFriendsComplex;
+
+ use My::Schema::User;
+ use base qw/My::Schema::User/;
+
+ __PACKAGE__->table('dummy'); # currently must be called before anything else
+
+ # Hand in your query as a scalar reference
+ # It will be added as a sub-select after FROM,
+ # so pay attention to the surrounding brackets!
+ __PACKAGE__->name( \<<SQL );
+ ( SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.user_id
+ WHERE f.friend_user_id = ?
+ UNION
+ SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.friend_user_id
+ WHERE f.user_id = ? )
+ SQL
+
+TIMTOWDI.
=head2 Using specific columns
__PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
+=head2 Filtering a relationship result set
+
+If you want to get a filtered result set, you can just add add to $attr as follows:
+
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
+
=head2 Many-to-many relationships
This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
generator to put the quotes the correct place.
In most cases you should set these as part of the arguments passed to
-L<DBIx::Class::Schema/conect>:
+L<DBIx::Class::Schema/connect>:
my $schema = My::Schema->connect(
'dbi:mysql:my_db',
The limit dialect can also be set at connect time by specifying a
C<limit_dialect> key in the final hash as shown above.
+=head2 Working with PostgreSQL array types
+
+If your SQL::Abstract version (>= 1.50) supports it, you can assign to
+PostgreSQL array values by passing array references in the C<\%columns>
+(C<\%vals>) hashref of the L<DBIx::Class::ResultSet/create> and
+L<DBIx::Class::Row/update> family of methods:
+
+ $resultset->create({
+ numbers => [1, 2, 3]
+ });
+
+ $row->update(
+ {
+ numbers => [1, 2, 3]
+ },
+ {
+ day => '2008-11-24'
+ }
+ );
+
+In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
+methods) you cannot directly use array references (since this is interpreted as
+a list of values to be C<OR>ed), but you can use the following syntax to force
+passing them as bind values:
+
+ $resultset->search(
+ {
+ numbers => \[ '= ?', [1, 2, 3] ]
+ }
+ );
+
+See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
+placeholders and bind values (subqueries)> for more explanation.
+
=head1 BOOTSTRAPPING/MIGRATING
=head2 Easy migration from class-based to schema-based setup
projects / dbsrgits/DBIx-Class.git / blobdiff