This document is intended as an anti-map of the documentation. If you
know what you want to do, but not how to do it in L<DBIx::Class>, then
-look here. It does B<not> contain any code or examples, it just gives
+look here. It does B<not> contain much code or examples, it just gives
explanations and pointers to the correct pieces of documentation to
read.
=item .. create a database to use?
First, choose a database. For testing/experimenting, we reccommend
-L<DBD::SQLite>, which is a self-contained small database. (i.e. all
-you need to do is to install the DBD from CPAN, and it's usable).
+L<DBD::SQLite>, which is a self-contained small database (i.e. all you
+need to do is to install L<DBD::SQLite> from CPAN, and it's usable).
Next, spend some time defining which data you need to store, and how
it relates to the other data you have. For some help on normalisation,
=item .. use DBIx::Class with L<Catalyst>?
-Install L<Catalyst::Model::DBIC::Schema> from CPAN. See it's
+Install L<Catalyst::Model::DBIC::Schema> from CPAN. See its
documentation, or below, for further details.
=item .. set up my DBIx::Class classes automatically from my database?
-Install L<DBIx::Class::Schema::Loader> from CPAN, and read it's documentation.
+Install L<DBIx::Class::Schema::Loader> from CPAN, and read its documentation.
=item .. set up my DBIx::Class classes manually?
-Look at the L<DBIx::Class::Manual::Example>, come back here if you get lost.
+Look at the L<DBIx::Class::Manual::Example> and come back here if you get lost.
=item .. create my database tables from my DBIx::Class schema?
L<DBIx::Class::Schema/deploy>. See there for details, or the
L<DBIx::Class::Manual::Cookbook>.
+=item .. connect to my database?
+
+Once you have created all the appropriate table/source classes, and an
+overall L<Schema|DBIx::Class::Schema> class, you can start using
+them in an application. To do this, you need to create a central
+Schema object, which is used to access all the data in the various
+tables. See L<DBIx::Class::Schema/connect> for details. The actual
+connection does not happen until you actually request data, so don't
+be alarmed if the error from incorrect connection details happens a
+lot later.
+
+
=back
=head2 Relationships
=item .. tell DBIx::Class about relationships between my tables?
-There are a vareity of relationship types that come pre-defined for you to use. These are all listed in L<DBIx::Class::Relationship>. If you need a non-standard type, or more information, look in L<DBIx::Class::Relationship::Base>.
+There are a vareity of relationship types that come pre-defined for
+you to use. These are all listed in L<DBIx::Class::Relationship>. If
+you need a non-standard type, or more information, look in
+L<DBIx::Class::Relationship::Base>.
=item .. define a one-to-many relationship?
-This is called a C<has_many> relationship on the one side, and a C<belongs_to> relationship on the many side. Currently these need to be set up individually on each side. See L<DBIx::Class::Relationship> for details.
+This is called a C<has_many> relationship on the one side, and a
+C<belongs_to> relationship on the many side. Currently these need to
+be set up individually on each side. See L<DBIx::Class::Relationship>
+for details.
=item .. define a relationship where this table contains another table's primary key? (foreign key)
-Create a C<belongs_to> relationship for the field containing the foreign key. L<DBIx::Class::Relationship/belongs_to>.
+Create a C<belongs_to> relationship for the field containing the
+foreign key. See L<DBIx::Class::Relationship/belongs_to>.
=item .. define a foreign key relationship where the key field may contain NULL?
-Just create a C<belongs_to> relationship, as above. If
-the column is NULL then the inflation to the foreign object will not
-happen. This has a side effect of not always fetching all the relevant
-data, if you use a nullable foreign-key relationship in a JOIN, then
-you probably want to set the join_type to 'left'.
+Just create a C<belongs_to> relationship, as above. If the column is
+NULL then the inflation to the foreign object will not happen. This
+has a side effect of not always fetching all the relevant data, if you
+use a nullable foreign-key relationship in a JOIN, then you probably
+want to set the C<join_type> to C<left>.
=item .. define a relationship where the key consists of more than one column?
By default, DBIx::Class cascades deletes and updates across
C<has_many> relationships. If your database already does this (and
-probably better), turn it off by supplying C<< cascade_delete => 0 >> in
-the relationship attributes. See L<DBIx::Class::Relationship::Base>.
+that is probably better), turn it off by supplying C<< cascade_delete => 0 >>
+in the relationship attributes. See L<DBIx::Class::Relationship::Base>.
=item .. use a relationship?
-Use it's name. An accessor is created using the name. See examples in L<DBIx::Class::Manual::Cookbook/Using relationships>.
+Use its name. An accessor is created using the name. See examples in
+L<DBIx::Class::Manual::Cookbook/Using relationships>.
=back
=item .. search for data?
+Create a C<$schema> object, as mentioned above in ".. connect to my
+database". Find the L<ResultSet|DBIx::Class::Manual::Glossary/ResultSet>
+that you want to search in, and call C<search> on it. See
+L<DBIx::Class::ResultSet/search>.
+
=item .. search using database functions?
+Supplying something like:
+
+ ->search({'mydatefield' => 'now()'})
+
+to search, will probably not do what you expect. It will quote the
+text "now()", instead of trying to call the function. To provide
+literal, unquoted text you need to pass in a scalar reference, like
+so:
+
+ ->search({'mydatefield' => \'now()'})
+
=item .. sort the results of my search?
+Supply a list of columns you want to sort by to the C<order_by>
+attribute. See L<DBIx::Class::ResultSet/order_by>.
+
+=item .. sort my results based on fields I've aliased using C<as>?
+
+You don't. You'll need to supply the same functions/expressions to
+C<order_by>, as you did to C<select>.
+
+To get "fieldname AS alias" in your SQL, you'll need to supply a
+literal chunk of SQL in your C<select> attribute, such as:
+
+ ->search({}, { select => [ \'now() AS currenttime'] })
+
+Then you can use the alias in your C<order_by> attribute.
+
=item .. group the results of my search?
+Supply a list of columns you want to group on, to the C<group_by>
+attribute, see L<DBIx::Class::ResultSet/group_by>.
+
+=item .. group my results based on fields I've aliased using C<as>?
+
+You don't. You'll need to supply the same functions/expressions to
+C<group_by>, as you did to C<select>.
+
+To get "fieldname AS alias" in your SQL, you'll need to supply a
+literal chunk of SQL in your C<select> attribute, such as:
+
+ ->search({}, { select => [ \'now() AS currenttime'] })
+
+Then you can use the alias in your C<group_by> attribute.
+
=item .. filter the results of my search?
+The first argument to C<search> is a hashref of accessor names and
+values to filter them by, for example:
+
+ ->search({'created_time' => { '>=', '2006-06-01 00:00:00' } })
+
+Note that to use a function here you need to make the whole value into
+a scalar reference:
+
+ ->search({'created_time' => \'>= yesterday()' })
+
=item .. search in several tables simultaneously?
+To search in two related tables, you first need to set up appropriate
+relationships between their respective classes. When searching you
+then supply the name of the relationship to the C<join> attribute in
+your search, for example when searching in the Books table for all the
+books by the author "Fred Bloggs":
+
+ ->search({'authors.name' => 'Fred Bloggs'}, { join => 'authors' })
+
+The type of join created in your SQL depends on the type of
+relationship between the two tables, see L<DBIx::Class::Relationship>
+for the join used by each relationship.
+
+=item .. create joins with conditions other than column equality?
+
+Currently, L<DBIx::Class> can only create join conditions using
+equality, so you're probably better off creating a C<view> in your
+database, and using that as your source. A C<view> is a stored SQL
+query, which can be accessed similarly to a table, see your database
+documentation for details.
+
+=item .. search using greater-than or less-than and database functions?
+
+To use functions or literal SQL with conditions other than equality
+you need to supply the entire condition, for example:
+
+ my $interval = "< now() - interval '12 hours'";
+ ->search({last_attempt => \$interval})
+
+and not:
+
+ my $interval = "now() - interval '12 hours'";
+ ->search({last_attempt => { '<' => \$interval } })
+
=item .. find more help on constructing searches?
Behind the scenes, DBIx::Class uses L<SQL::Abstract> to help construct
-it's SQL searches. So if you fail to find help in the
+its SQL searches. So if you fail to find help in the
L<DBIx::Class::Manual::Cookbook>, try looking in the SQL::Abstract
documentation.
=over 4
-=item .. fetch as much data as possible in as few select calls as possible? (prefetch)
+=item .. fetch as much data as possible in as few select calls as possible?
+
+See the prefetch examples in the L<Cookbook|DBIx::Class::Manual::Cookbook>.
+
+=item .. fetch a whole column of data instead of a row?
+
+Call C<get_column> on a L<DBIx::Class::ResultSet>, this returns a
+L<DBIx::Class::ResultSetColumn>, see it's documentation and the
+L<Cookbook|DBIx::Class::Manual::Cookbook> for details.
+
+=item .. fetch a formatted column?
+
+In your table schema class, create a "private" column accessor with:
-See the prefetch examples in the L<DBIx::Class::Manual::Cookbook|"Cookbook">.
+ __PACKAGE__->add_columns(my_common => { accessor => '_hidden_my_column' });
+
+Then, in the same class, implement a subroutine called "my_column" that
+fetches the real value and does the formatting you want.
+
+See the Cookbook for more details.
+
+=item .. fetch a single (or topmost) row?
+
+Sometimes you many only want a single record back from a search. A quick
+way to get that single row is to first run your search as usual:
+
+ ->search->(undef, { order_by => "id DESC" })
+
+Then call L<DBIx::Class::ResultSet/slice> and ask it only to return 1 row:
+
+ ->slice(0,1)
+
+These two calls can be combined into a single statement:
+
+ ->search->(undef, { order_by => "id DESC" })->slice(0,1)
+
+Why slice instead of L<DBIx::Class::ResultSet/first> or L<DBIx::Class::ResultSet/single>?
+If supported by the database, slice will use LIMIT/OFFSET to hint to the database that we
+really only need one row. This can result in a significant speed improvement.
=back
=over 4
+=item .. insert a row with an auto incrementing primary key?
+
+In versions of L<DBIx::Class> less than 0.07, you need to ensure your
+table class loads the L<PK::Auto|DBIx::Class::PK::Auto>
+component. This will attempt to fetch the value of your primary key
+from the database after the insert has happened, and store it in the
+created object. In versions 0.07 and above, this component is
+automatically loaded.
+
+=item .. insert a row with a primary key that uses a sequence?
+
+You need to create a trigger in your database that updates your
+primary key field from the sequence. To help PK::Auto find your
+inserted key, you can tell it the name of the sequence in the
+C<column_info> supplied with C<add_columns>.
+
+ ->add_columns({ id => { sequence => 'mysequence' } });
+
=item .. insert many rows of data efficiently?
=item .. update a collection of rows at the same time?
+Create a resultset using a search, to filter the rows of data you
+would like to update, then call update on the resultset to change all
+the rows at once.
+
=item .. use database functions when updating rows?
=item .. update a column using data from another column?
+To stop the column name from being quoted, you'll need to supply a
+scalar reference:
+
+ ->update({ somecolumn => \'othercolumn' })
+
+=item .. store JSON/YAML in a column and have it deflate/inflate automatically?
+
+You can use L<DBIx::Class::InflateColumn> to accomplish YAML/JSON storage transparently.
+
+If you want to use JSON, then in your table schema class, do the following:
+
+ use JSON;
+
+ __PACKAGE__->add_columns(qw/ ... my_column ../)
+ __PACKAGE__->inflate_column('my_column', {
+ inflate => sub { jsonToObj(shift) },
+ deflate => sub { objToJson(shift) },
+ });
+
+For YAML, in your table schema class, do the following:
+
+ use YAML;
+
+ __PACKAGE__->add_columns(qw/ ... my_column ../)
+ __PACKAGE__->inflate_column('my_column', {
+ inflate => sub { YAML::Load(shift) },
+ deflate => sub { YAML::Dump(shift) },
+ });
+
+This technique is an easy way to store supplemental unstructured data in a table. Be
+careful not to overuse this capability, however. If you find yourself depending more
+and more on some data within the inflated column, then it may be time to factor that
+data out.
+
=back
=head2 Misc
=item How do I store my own (non-db) data in my DBIx::Class objects?
-=item How do I use DBIx::Class objects my TT templates?
+You can add your own data accessors to your classes.
+
+=item How do I use DBIx::Class objects in my TT templates?
+
+Like normal objects, mostly. However you need to watch out for TT
+calling methods in list context. When calling relationship accessors
+you will not get resultsets, but a list of all the related objects.
+
+Starting with version 0.07, you can use L<DBIx::Class::ResultSet/search_rs>
+to work around this issue.
=item See the SQL statements my code is producing?
+Turn on debugging! See L<DBIx::Class::Storage> for details of how
+to turn on debugging in the environment, pass your own filehandle to
+save debug to, or create your own callback.
+
=item Why didn't my search run any SQL?
+L<DBIx::Class> runs the actual SQL statement as late as possible, thus
+if you create a resultset using C<search> in scalar context, no query
+is executed. You can create further resultset refinements by calling
+search again or relationship accessors. The SQL query is only run when
+you ask the resultset for an actual row object.
+
+=back
+
+=head2 Notes for CDBI users
+
+=over 4
+
+=item Is there a way to make an object auto-stringify itself as a
+particular column or group of columns (a-la cdbi Stringfy column
+group, or stringify_self method) ?
+
+See L<Cookbook/Stringification>
=back
projects / dbsrgits/DBIx-Class.git / blobdiff