ActiveRecord强大的find()方法实践

实践了ActiveRecord的find方法，要实现多张表的联合查询，方法如下：

 

class Product < ActiveRecord::Base
 
  def Product .find_by_ user( user _id)    #相当于self.find_by_user(user_id) ...类级别的函数

 

    Product .find(:all ,
                 :select => "products.name pname, users.name uname, products.position_id, 

                                    products.summary, positions.title ",
                 :from => "products, users, positions ",
                 :conditions => ["products. user _id = user s.id and products.position_id = positions.id and 

                                            user s.id = ?" , user _id],
                 :order       => "products.id DESC ")
  end  

 

end

 

当然还有更直接的方法，那就是ActiveRecord的find_by_sql() 方法。

此方法直接将SQL语句用字符串的形式传进去就行了，举两个例子：

orders = Order.find_by_sql("select * from orders");

orders = Order.find_by_sql("select * from orders where id = ?", order_id);