Hi, here’s a snippet from section 17.5 of ‘Agile Web Development with Rails 2ed’.
:joins The :joins parameter to the finder method lets you specify a list of additional tables to be joined to the default table. This parameter is inserted into the SQL immediately after the name of the model’s table and before any conditions specified by the first parameter. The join syntax is database-specific. The
CRUD—CREATE, READ, UPDATE, DELETE 286 following code returns a list of all line items for the book called Programming Ruby.
LineItem.find(:all, :conditions => “pr.title = ‘Programming Ruby’”, :joins => “as li inner join products as pr on li.product_id = pr.id”)
As we’ll see in Chapter 18, Active Record Part II Relationships Between Tables, on page 306, you probably won’t use the :joins parameter of find( ) very much—Active Record handles most of the common intertable joins for you.
Good luck,
-Conrad
