thanks all... problem solved. 2009/7/3 Colin Law <[email protected]>
> > 2009/7/3 gaoxh gaoxh04 <[email protected]>: > > If I remove id column, what is the primary key? > > Have a look at the rails guides, particularly the one on ActiveRecord > associations at http://guides.rubyonrails.org/index.html > > Colin > > > > > 2009/7/3 Marnen Laibow-Koser <[email protected]> > >> > >> Xiahong Gao wrote: > >> > Hi everyone, > >> > > >> > I ran into a serious problem when I was trying to do something similar > >> > to twitter follow mechanism. The thing is like this: > >> > > >> > First, I have a self-referential table, named "users" > >> > create_table :users do |t| > >> > t.column :name, :string > >> > t.column :user_name, :string > >> > t.column :password, :string > >> > t.column :email, :string > >> > end > >> > > >> > I also have a HABTM join table, named "follow_relations" > >> > create_table :follow_realtions do |t| > >> > t.column :a_id, :integer # a_id follows b_id > >> > t.column :b_id, :integer > >> > end > >> > > >> > My HABTM join is defined as follows > >> > has_and_belongs_to_many :followers, > >> > :class_name => > >> > "User", > >> > :join_table => > >> > "follow_relations", > >> > :foreign_key => > >> > "b_id", > >> > > >> > :association_foreign_key > >> > => "a_id" > >> > > >> > has_and_belongs_to_many :followings, > >> > :class_name => "User", > >> > :join_table => > >> > "follow_relations", > >> > :foreign_key => > >> > "a_id", > >> > > :association_foreign_key > >> > => "b_id" > >> [...] > >> > The first << operation executes the following SQL : > >> > INSERT INTO `follow_relations (`id`, `b_id`, `a_id`) VALUES (3, 1, 3) > >> > The second << operation executes the following SQL: > >> > INSERT INTO `follow_relations (`id`, `b_id`, `a_id`) VALUES (3, 2, 3) > >> > Thus, key id is duplicated. It looks like that every time, the value > >> > of column id is copied from column a_id. > >> > What's going on here? How to fix this problem? > >> > >> If you're using HABTM, the join table (follow_relations) should not have > >> an id column. Remove it and see if that does the trick. > >> > >> > > >> > Thanks in advance, > >> > xiahong > >> > >> Best, > >> -- > >> Marnen Laibow-Koser > >> http://www.marnen.org > >> [email protected] > >> -- > >> Posted via http://www.ruby-forum.com/. > >> >> > > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
