# Has\_many or HABTM? **URL:** \ **Category:** Rails\ **Created:** [November 28, 2005, 1:29am UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976 "2005-11-28T01:29:18Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![i8ramin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/e36b37/32.png) [@i8ramin](https://www.ruby-forum.com/u/i8ramin)\ **Post date:** [November 28, 2005, 1:29am UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976/1 "2005-11-28T01:29:18Z")
I can’t determine whether I should be using has\_many or has\_and\_belongs\_to\_many. I am creating a community type site with users. Users can add other users to their favorites or bookmark them. So each user has many favorites. Each favorite is actually another User and not another object or model, so I can’t have a favorites\_users table. I user model currently looks like this: class User \< ActiveRecord::Base has\_and\_belongs\_to\_many :favorites, :join\_table =\> ‘favorites’, :class\_name =\> ‘User’, :foreign\_key =\> ‘user\_id’, :association\_foreign\_key =\> ‘favorite\_id’ end and I have a favorites table in my db, defined as: CREATE TABLE `favorites` ( `user_id` int(10) NOT NULL default ‘0’, `favorite_id` int(10) NOT NULL default ‘0’, `created_on` datetime default NULL, PRIMARY KEY (`user_id`,`favorite_id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; Is this correct or can I just use has\_many :favorites? Thanks ---
**Author:** ![i8ramin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/e36b37/32.png) [@i8ramin](https://www.ruby-forum.com/u/i8ramin)\ **Post date:** [November 28, 2005, 1:45am UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976/2 "2005-11-28T01:45:24Z")
On 11/28/05, Ramin [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > :join_table => 'favorites', > > ``` > > `created_on` datetime default NULL, > PRIMARY KEY (`user_id`,`favorite_id`) > ) ENGINE=MyISAM DEFAULT CHARSET=utf8; > > Is this correct or can I just use has\_many :favorites? Take a look at this [http://wiki.rubyonrails.com/rails/pages/HowToUseManyToManyAgainstASingleTable](http://wiki.rubyonrails.com/rails/pages/HowToUseManyToManyAgainstASingleTable) ---
**Author:** ![i8ramin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/e36b37/32.png) [@i8ramin](https://www.ruby-forum.com/u/i8ramin)\ **Post date:** [November 28, 2005, 1:49am UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976/3 "2005-11-28T01:49:27Z")
In all those examples they are using HABTM, so I guess I’m doing it right… it works fine enough. I was just wondering if the same thing could be done with just has\_many. On 11/27/05, Rodrigo A. Fernández [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > CREATE TABLE `favorites` ( > > [Peak Obsession](http://wiki.rubyonrails.com/rails/pages/HowToUseManyToManyAgainstASingleTable) > > * * * > > Rails mailing list > removed\_email\_address@domain.invalid > [http://lists.rubyonrails.org/mailman/listinfo/rails](http://lists.rubyonrails.org/mailman/listinfo/rails) – - Ramin [http://www.getintothis.com/blog](http://www.getintothis.com/blog) ---
**Author:** ![i8ramin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/e36b37/32.png) [@i8ramin](https://www.ruby-forum.com/u/i8ramin)\ **Post date:** [November 28, 2005, 1:23pm UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976/4 "2005-11-28T13:23:38Z")
On 28.11.2005, at 2.47, Ramin wrote: > In all those examples they are using HABTM, so I guess I’m doing it > right… it works fine enough. I was just wondering if the same thing > could be done with just has\_many. Yes, it could, if you’d created a class for favorites. Then you’d have two has\_many relationships between user and favorite classes (‘favorites’ and ‘people who’ve made me a favorite’). Of course, if you only need it one way, you’ll be fine with just a single relationship. //jarkko ---
**Author:** ![i8ramin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/e36b37/32.png) [@i8ramin](https://www.ruby-forum.com/u/i8ramin)\ **Post date:** [November 28, 2005, 10:14pm UTC](https://www.ruby-forum.com/t/has-many-or-habtm/48976/5 "2005-11-28T22:14:29Z")
For most things, I’m moving away from HABTM. It is a very nice, simple solution in some cases. However, it has limitations and other things that make it ‘not-so-nice’ in real usage (sometimes). You’ll probably find it nice to have an ‘id’ associated with a particular favorite. Be it for deleting or otherwise, having this explicit is useful to indicate exactly -which- favorite you’re referring to. HABTM works best without this associated ‘id’ and also works best if the join table only has two foreign keys and no ancillary data. The docs say it could have ancillary data, but the construction isn’t the best – ancillary data gets blasted when you use :include to eager load some things. (you may want to use ancillary data like a comment that gets associated with each favorite or something, but then use eager loading to load the other-user’s account group name (or something). Near as I can tell, this is broken. You also gain a few other advantages by defining a new model for your favorites. Validations, for example. Anyway, that’s my take. I still use HABTM, but only in very specific cases where all I want is a clean, simple, association. Jake i8ramin wrote: > I can’t determine whether I should be using has\_many or > has\_and\_belongs\_to\_many. I am creating a community type site with > users. Users can add other users to their favorites or bookmark them. > So each user has many favorites. Each favorite is actually another > User and not another object or model, so I can’t have a > favorites\_users table. I user model currently looks like this: > > class User \< ActiveRecord::Base > has\_and\_belongs\_to\_many :favorites, > :join\_table =\> ‘favorites’, > :class\_name =\> ‘User’, > :foreign\_key =\> ‘user\_id’, > :association\_foreign\_key =\> ‘favorite\_id’ > end > > and I have a favorites table in my db, defined as: > > CREATE TABLE `favorites` ( > `user_id` int(10) NOT NULL default ‘0’, > `favorite_id` int(10) NOT NULL default ‘0’, > `created_on` datetime default NULL, > PRIMARY KEY (`user_id`,`favorite_id`) > ) ENGINE=MyISAM DEFAULT CHARSET=utf8; > > Is this correct or can I just use has\_many :favorites? > > Thanks