Rails 3 的active record和其他
今天，徘徊在几个问题之间简单流水帐，复制一下

现在的Rails版本是3.0.7
看active record呢

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html
http://api.rubyonrails.org/classes/ActiveRecord/Base.html

上面的官网API看起来很不错
之前版本如下

http://ar.rubyonrails.org/classes/ActiveRecord/Base.html

Company.where(  "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",  { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }).firstStudent.where(:first_name => "Harvey", :status => 1)Student.where(params[:student])User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }]) do |u|  u.is_admin = falseendPost.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]> [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]

关于relation

TreeMixin.find :all, :joins => :children# => SELECT ... FROM mixins INNER JOIN mixins childrens_mixins ...TreeMixin.find :all, :joins => {:children => :parent}# => SELECT ... FROM mixins INNER JOIN mixins childrens_mixins ...                            INNER JOIN parents_mixins ...TreeMixin.find :all, :joins => {:children => {:parent => :children}}# => SELECT ... FROM mixins INNER JOIN mixins childrens_mixins ...                            INNER JOIN parents_mixins ...                            INNER JOIN mixins childrens_mixins_2

在rails 3下卸载active record