July 20, 2010

Rails HasAndBelongsToMany Association With Primary Key Error

When using has_and_belongs_to_many, I ran into this error,

Primary key is not allowed in a has_and_belongs_to_many join table (articles_users).

So check the linked-table , articles_users in my case, if there is a pk set by default.


Put the :id => false to the migration create_table SQL.

create_table :articles_users, :id => false do |t|
  t.integer :article_id
  t.integer :user_id
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Qihuan Piao

Qihuan Piao

(aka kinopyo) is Chinese based in Tokyo. Software writer. He shares stories inspired him in this blog. His infamous line - "I feel calm when I kill those monsters, or people (in game)" shocks his friends deeply.

He also writes in Japanese and Chinese.