diff options
Diffstat (limited to 'railties/guides/source/active_record_querying.textile')
| -rw-r--r-- | railties/guides/source/active_record_querying.textile | 56 |
1 files changed, 49 insertions, 7 deletions
diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile index e3871a3c34..082f9eda7d 100644 --- a/railties/guides/source/active_record_querying.textile +++ b/railties/guides/source/active_record_querying.textile @@ -256,7 +256,7 @@ The above will yield the supplied block with +1000+ invoices every time. h3. Conditions -The +find+ method allows you to specify conditions to limit the records returned, representing the +WHERE+-part of the SQL statement. Conditions can either be specified as a string, array, or hash. +The +where+ method allows you to specify conditions to limit the records returned, representing the +WHERE+-part of the SQL statement. Conditions can either be specified as a string, array, or hash. h4. Pure String Conditions @@ -466,7 +466,7 @@ To apply a +GROUP BY+ clause to the SQL fired by the finder, you can specify the For example, if you want to find a collection of the dates orders were created on: <ruby> -Order.group("date(created_at)").order("created_at") +Order.select("date(created_at) as ordered_date, sum(price) as total_price").group("date(created_at)") </ruby> And this will give you a single +Order+ object for each date where there are orders in the database. @@ -474,7 +474,7 @@ And this will give you a single +Order+ object for each date where there are ord The SQL that would be executed would be something like this: <sql> -SELECT * FROM orders GROUP BY date(created_at) ORDER BY created_at +SELECT date(created_at) as ordered_date, sum(price) as total_price FROM orders GROUP BY date(created_at) </sql> h3. Having @@ -484,16 +484,16 @@ SQL uses the +HAVING+ clause to specify conditions on the +GROUP BY+ fields. You For example: <ruby> -Order.group("date(created_at)").having("created_at < ?", 1.month.ago) +Order.select("date(created_at) as ordered_date, sum(price) as total_price").group("date(created_at)").having("sum(price) > ?", 100) </ruby> The SQL that would be executed would be something like this: <sql> -SELECT * FROM orders GROUP BY date(created_at) HAVING created_at < '2011-04-27' +SELECT date(created_at) as ordered_date, sum(price) as total_price FROM orders GROUP BY date(created_at) HAVING sum(price) > 100 </sql> -This will return single order objects for each day, but only those that are at least one month old. +This will return single order objects for each day, but only those that are ordered more than $100 in a day. h3. Overriding Conditions @@ -965,6 +965,47 @@ Using a class method is the preferred way to accept arguments for scopes. These category.posts.1_week_before(time) </ruby> +h4. Working with scopes + +Where a relational object is required, the +scoped+ method may come in handy. This will return an +ActiveRecord::Relation+ object which can have further scoping applied to it afterwards. A place where this may come in handy is on associations + +<ruby> +client = Client.find_by_first_name("Ryan") +orders = client.orders.scoped +</ruby> + +With this new +orders+ object, we are able to ascertain that this object can have more scopes applied to it. For instance, if we wanted to return orders only in the last 30 days at a later point. + +<ruby> +orders.where("created_at > ?", 30.days.ago) +</ruby> + +h4. Applying a default scope + +If we wish for a scope to be applied across all queries to the model we can use the +default_scope+ method within the model itself. + +<ruby> +class Client < ActiveRecord::Base + default_scope where("removed_at IS NULL") +end +</ruby> + +When queries are executed on this model, the SQL query will now look something like this: + +<sql> +SELECT * FROM clients WHERE removed_at IS NULL +</sql> + +h4. Removing all scoping + +If we wish to remove scoping for any reason we can use the +unscoped+ method. This is especially useful if a +default_scope+ is specified in the model and should not be applied for this particular query. + +<ruby> +Client.unscoped.all +</ruby> + +This method removes all scoping and will do a normal query on the table. + h3. Dynamic Finders For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called +first_name+ on your +Client+ model for example, you get +find_by_first_name+ and +find_all_by_first_name+ for free from Active Record. If you have a +locked+ field on the +Client+ model, you also get +find_by_locked+ and +find_all_by_locked+ methods. @@ -1146,7 +1187,8 @@ For options, please see the parent section, "Calculations":#calculations. h3. Changelog -* December 23 2010: Add documentation for the +scope+ method. "Ryan Bigg":http://ryanbigg.com +* June 26 2011: Added documentation for the +scoped+, +unscoped+ and +default+ methods. "Ryan Bigg":credits.html#radar +* December 23 2010: Add documentation for the +scope+ method. "Ryan Bigg":credits.html#radar * April 7, 2010: Fixed document to validate XHTML 1.0 Strict. "Jaime Iniesta":http://jaimeiniesta.com * February 3, 2010: Update to Rails 3 by "James Miller":credits.html#bensie * February 7, 2009: Second version by "Pratik":credits.html#lifo |