diff options
Diffstat (limited to 'railties/guides/source/active_record_querying.textile')
| -rw-r--r-- | railties/guides/source/active_record_querying.textile | 17 |
1 files changed, 5 insertions, 12 deletions
diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile index b112c4f5fb..302dad4f1a 100644 --- a/railties/guides/source/active_record_querying.textile +++ b/railties/guides/source/active_record_querying.textile @@ -6,7 +6,6 @@ This guide covers different ways to retrieve data from the database using Active * Specify the order, retrieved attributes, grouping, and other properties of the found records * Use eager loading to reduce the number of database queries needed for data retrieval * Use dynamic finders methods -* Create named scopes to add custom finding behavior to your models * Check for the existence of particular records * Perform various calculations on Active Record models @@ -23,7 +22,6 @@ TIP: All of the following models uses +id+ as the primary key, unless specified <ruby> class Client < ActiveRecord::Base has_one :address - has_one :mailing_address has_many :orders has_and_belongs_to_many :roles end @@ -36,11 +34,6 @@ end </ruby> <ruby> -class MailingAddress < Address -end -</ruby> - -<ruby> class Order < ActiveRecord::Base belongs_to :client, :counter_cache => true end @@ -245,7 +238,7 @@ WARNING: Building your own conditions as pure strings can leave you vulnerable t h4. Array Conditions -Now what if that number could vary, say as a argument from somewhere, or perhaps from the user's level status somewhere? The find then becomes something like: +Now what if that number could vary, say as an argument from somewhere, or perhaps from the user's level status somewhere? The find then becomes something like: <ruby> Client.first(:conditions => ["orders_count = ?", params[:orders]]) @@ -465,7 +458,7 @@ Be careful because this also means you're initializing a model object with only ActiveRecord::MissingAttributeError: missing attribute: <attribute> </shell> -Where +<attribute>+ is the attribute you asked for. The +id+ method will not raise the +ActiveRecord::MissingAttributeError+, so just be careful when working with associations because they need the +id+ method to function properly. +Where +<attribute>+ is the attribute you asked for. The +id+ method will not raise the +ActiveRecord::MissingAttributeError+, so just be careful when working with associations because they need the +id+ method to function properly. You can also call SQL functions within the select option. For example, if you would like to only grab a single record per unique value in a certain field by using the +DISTINCT+ function you can do it like this: @@ -539,7 +532,7 @@ This will return single order objects for each day, but only for the last month. h4. Readonly Objects -To explicitly disallow modification/destroyal of the matching records returned by +Model.find+, you could specify the +:readonly+ option as +true+ to the find call. +To explicitly disallow modification/destruction of the matching records returned by +Model.find+, you could specify the +:readonly+ option as +true+ to the find call. Any attempt to alter or destroy the readonly records will not succeed, raising an +ActiveRecord::ReadOnlyRecord+ exception. To set this option, specify it like this: @@ -807,12 +800,12 @@ For every field (also known as an attribute) you define in your table, Active Re You can do +find_last_by_*+ methods too which will find the last record matching your argument. -You can specify an exclamation point (!) on the end of the dynamic finders to get them to raise an +ActiveRecord::RecordNotFound+ error if they do not return any records, like +Client.find_by_name!("Ryan")+ +You can specify an exclamation point (<tt>!</tt>) on the end of the dynamic finders to get them to raise an +ActiveRecord::RecordNotFound+ error if they do not return any records, like +Client.find_by_name!("Ryan")+ If you want to find both by name and locked, you can chain these finders together by simply typing +and+ between the fields for example +Client.find_by_name_and_locked("Ryan", true)+. -There's another set of dynamic finders that let you find or create/initialize objects if they aren't found. These work in a similar fashion to the other finders and can be used like +find_or_create_by_name(params[:name])+. Using this will firstly perform a find and then create if the find returns nil. The SQL looks like this for +Client.find_or_create_by_name("Ryan")+: +There's another set of dynamic finders that let you find or create/initialize objects if they aren't found. These work in a similar fashion to the other finders and can be used like +find_or_create_by_name(params[:name])+. Using this will firstly perform a find and then create if the find returns +nil+. The SQL looks like this for +Client.find_or_create_by_name("Ryan")+: <sql> SELECT * FROM clients WHERE (clients.name = 'Ryan') LIMIT 1 |