# M:n or multiple 1:n? **URL:** \ **Category:** Rails\ **Created:** [March 7, 2006, 2:43pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514 "2006-03-07T14:43:10Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 7, 2006, 2:43pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/1 "2006-03-07T14:43:10Z")
I have a Newbee question: i have three tables and want to connect them. so is it stupid to make a triple m:n (rails style xs\_ys\_zs) or do i have to make a new table (newtable) where i got multiple 1:n? the habtm (has and belongs to many) do only work proper to join two tables, or i am wrong? -jens ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 7, 2006, 2:54pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/2 "2006-03-07T14:54:59Z")
Jens K. wrote: > i have three tables and want to connect them. so is it stupid to make a > triple m:n (rails style xs\_ys\_zs) or do i have to make a new table > (newtable) where i got multiple 1:n? It depends on whether you want the join table to have attributes. If you do, or think you might in the future, then you need a join model (with the appropriate table). It’s a little messier, but has\_many :through coming in Rails 1.1 makes life easier. Otherwise, you can get away with HABTM. > the habtm (has and belongs to many) do only work proper to join two > tables, or i am wrong? Yes, only two. Cheers! Tom ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 7, 2006, 3:32pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/3 "2006-03-07T15:32:33Z")
Tom T. wrote: > Jens K. wrote: > > > i have three tables and want to connect them. so is it stupid to make a > > triple m:n (rails style xs\_ys\_zs) or do i have to make a new table > > (newtable) where i got multiple 1:n? > > It depends on whether you want the join table to have attributes. If you > do, or think you might in the future, then you need a join model (with > the appropriate table). It’s a little messier, but has\_many :through > coming in Rails 1.1 makes life easier. > > Otherwise, you can get away with HABTM. how i can read attributes stored in the join table? M:N Table user\_id link\_id text \<- how i can read out this value updated\_at \<- how i can read out this value created\_at \<- how i can read out this value is it user.text or link.text? > > the habtm (has and belongs to many) do only work proper to join two > > tables, or i am wrong? > > Yes, only two. > > Cheers! > > Tom ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 7, 2006, 4:39pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/4 "2006-03-07T16:39:28Z")
Jens K. wrote: > how i can read attributes stored in the join table? > > M:N Table > user\_id > link\_id > text \<- how i can read out this value > updated\_at \<- how i can read out this value > created\_at \<- how i can read out this value > > is it user.text or link.text? Just access it as a normal model. @a = JoinModel.find :first @a.text You can also access it through the models it belongs to, such as user.join\_models… Cheers! Tom ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 8, 2006, 5:47pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/5 "2006-03-08T17:47:45Z")
I do not understand it. I have installed the login\_engine plugin. There I put the has\_and\_belongs\_to\_many :links In the link model I put the has\_and\_belongs\_to\_many :users Rails do not recognize the links\_users table. Why? ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 7, 2006, 9:15pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/6 "2006-03-07T21:15:17Z")
That’s that easy? whow, i will test it tomorrow! cheers! -Jens > Just access it as a normal model. > > @a = JoinModel.find :first > @a.text > > You can also access it through the models it belongs to, such as > user.join\_models… > > Cheers! > > Tom ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 8, 2006, 7:12pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/7 "2006-03-08T19:12:04Z")
Jens, I recently switched from login\_engine to the acts\_as\_authenticated plugin based on this article: [http://glu.ttono.us/articles/2006/02/06/rails-best-practices-tips-and-tricks](http://glu.ttono.us/articles/2006/02/06/rails-best-practices-tips-and-tricks) and my experiences with login\_engine. You might want to consider acts\_as\_authenticated. ---
**Author:** ![krahe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/df705f/32.png) [@krahe](https://www.ruby-forum.com/u/krahe)\ **Post date:** [March 8, 2006, 9:55pm UTC](https://www.ruby-forum.com/t/m-n-or-multiple-1-n/54514/8 "2006-03-08T21:55:57Z")
Brian D. wrote: > Jens, I recently switched from login\_engine to the acts\_as\_authenticated > plugin based on this article: > [http://glu.ttono.us/articles/2006/02/06/rails-best-practices-tips-and-tricks](http://glu.ttono.us/articles/2006/02/06/rails-best-practices-tips-and-tricks) > > and my experiences with login\_engine. You might want to consider > acts\_as\_authenticated. Thanks Brian, I currently go away from M:N. I will try acts\_as\_authenticated. So will do multiple 1:N on one table like David Heinemeier wrote ([http://article.gmane.org/gmane.comp.lang.ruby.rails/32742/](http://article.gmane.org/gmane.comp.lang.ruby.rails/32742/)). So I can use :though when Rails 1.1 comes up. Rails is really great, but when a complex data model is on duty it’s anything than easy… when you want to store M:N’s you have to add this on scaffolding def create @link = Link.new(params[:link]) if @link.save @link.users = User.find\_by\_ **Something** @link.update\_attributes(params[:link]) flash[:notice] = ‘Link was successfully created.’ redirect\_to :action =\> ‘list’ else render :action =\> ‘new’ end end