ruby on rails - Do I need to create an assocation table for a :has_many :through association? -

i'm trying use :has_many :through type association, i'm getting following error:

activerecord::statementinvalid: sqlite3::sqlexception: no such column: work_units.developer_id: 

many other posts sort of thing have had spelling mistakes, i've checked mine.

class developer < activerecord::base   attr_accessible :skype_name, :language_ids, :user_attributes    has_many :work_units   has_many :projects, :through => :work_units   ... end  class project < activerecord::base   attr_accessible :complete, :description, :finalised, :price    has_many :work_units   has_many :developers, :through => :work_units   ... end  class workunit < activerecord::base   attr_accessible :hours_worked    belongs_to :project   belongs_to :developer end 

i've run db:migrate , didn't complain. did make mistake , had rollback db re-migrate, think did right. use annotate gem , doesn't show of relationship ids i'd expect. so, need create workunits table or missing something? rails guide didn't mention manually making tables.

edit

here's migration used create workunit model , stuff:

class createworkunits < activerecord::migration   def change     create_table :work_units |t|       t.integer :hours_worked, :default => 0       t.timestamps     end   end end 

edit 2

snippets schema.rb:

create_table "work_units", :force => true |t|   t.integer  "hours_worked", :default => 0   t.datetime "created_at",                  :null => false   t.datetime "updated_at",                  :null => false end  create_table "projects", :force => true |t|   t.string   "description"   t.decimal  "price",       :precision => 8, :scale => 2   t.boolean  "complete",    :default => false   t.datetime "created_at",  :null => false   t.datetime "updated_at",  :null => false end 

similarly :developers. so, why doesn't migration add association information me?

you need add foreign keys work_units table.

class createworkunits < activerecord::migration   def change     create_table :work_units |t|       t.integer :hours_worked, :default => 0       t.integer :project_id, null: false       t.integer :developer_id, null: false       t.timestamps     end      add_index :work_units, :project_id     add_index :work_units, :developer_id   end end 

another way:

class createworkunits < activerecord::migration   def change     create_table :work_units |t|       t.integer :hours_worked, :default => 0       t.belongs_to :project       t.belongs_to :developer       t.timestamps     end      add_index :work_units, :project_id     add_index :work_units, :developer_id   end end 

you can define these fields when generating model, they'll added migration automatically show in second snippet.

$ rails g model workunit hours_worked:integer project:belongs_to developer:belongs_to 

hope helps.