Run a SQL query within Ruby on Rails

ActiveRecord::Base.connection.execute(your_sql_statement)

Rail's ActiveRecord: include vs join

Confused when to use the :include vs. :join option? Remember these points:

• join does not load the association into association
• include does, it loads each association into memory
• include is not compatible with select option
• use include when the association is referenced
• example use with join, doing a dynamic count on an association
• or when the association is not referenced

ActiveRecord::Base#becomes

An ActiveRecord method I did not existed: becomes.

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes(Company) to render that instance using the companies/company partial instead of clients/client. Note: The new instance will share a link to the same attributes as the original class. So any change to the attributes in either instance will affect the other.

Custom default attribute in ActiveRecord

When I need a default value for a ActiveRecord attribute often I will resort to using a plugin. But in reality, initializing an attribute in the #after_initialize callback is often the simplest thing that works:

class Tweet
  def after_initialize
    self.message ||= "I'm Tweeting"
  end
end         

How to get the options for a named_scope

class Video < ActiveRecord::Base
  named_scope :highest_scores, :order => "score DESC, id"
end

Video.highest_scores.proxy_options # => {:order=>"score DESC, id"}

Class Methods Called Against Associations in Active Record

Did you know you can call class methods against associations? Admittedly this is a trivial example, but here goes:

Class methods also work against named scopes. I will provide a "good" example of this later in the week.