# Compose\_primary\_keys

**URL:** <https://www.ruby-forum.com/t/compose-primary-keys/171443>\
**Category:** Rails\
**Created:** [July 2, 2009, 2:45pm UTC](https://www.ruby-forum.com/t/compose-primary-keys/171443 "2009-07-02T14:45:19Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Augustus\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d9b06d/32.png) [@Augustus\_C](https://www.ruby-forum.com/u/Augustus_C)\
**Post date:** [July 2, 2009, 2:45pm UTC](https://www.ruby-forum.com/t/compose-primary-keys/171443/1 "2009-07-02T14:45:19Z")

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I´m looking for a way to work with compose primary keys.  
I alredy know that plugin [http://compositekeys.rubyforge.org/](http://compositekeys.rubyforge.org/)  
but it doesn´t have examples.

Please help =]

–  
Horus Augustus C. C. Lima

Sagarana Tech  
Mobile +55(85)8842.4402  
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<div class="post-metadata">

**Author:** ![Augustus\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d9b06d/32.png) [@Augustus\_C](https://www.ruby-forum.com/u/Augustus_C)\
**Post date:** [July 3, 2009, 1:43am UTC](https://www.ruby-forum.com/t/compose-primary-keys/171443/2 "2009-07-03T01:43:29Z")

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Augustus C. wrote:

> I´m looking for a way to work with compose primary keys.  
> I alredy know that plugin [http://compositekeys.rubyforge.org/](http://compositekeys.rubyforge.org/)  
> but it doesn´t have examples.  
> What do you mean it doesn’t have examples? What is this:

class Membership \< ActiveRecord::Base

# set\_primary\_keys \*keys - turns on composite key functionality

set\_primary\_keys :user\_id, :group\_id  
belongs\_to :user  
belongs\_to :group  
has\_many :statuses, :class\_name =\> ‘MembershipStatus’, :foreign\_key =\>  
[:user\_id, :group\_id]  
end

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<div class="post-metadata">

**Author:** ![Augustus\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d9b06d/32.png) [@Augustus\_C](https://www.ruby-forum.com/u/Augustus_C)\
**Post date:** [July 4, 2009, 1:38am UTC](https://www.ruby-forum.com/t/compose-primary-keys/171443/3 "2009-07-04T01:38:28Z")

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there’s a Google group “Composite Keys for ActiveRecord” that you  
might look at for tips