Databases
StackOverflow2013
Postsdbo
POSpecifying the foreign key in a has_many :through relationship
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POSpecifying the foreign key in a has_many :through relationship
    primarykey
    data
    text
    <p>I have the following three models: User, Project, and Assignment.</p> <p>A User <code>has_many</code> Projects through an assignment. However, Assignment actually has <em>two</em> foreign keys that relate to a User: <code>user_id</code> (representing the user who was assigned the project) and <code>completer_id</code> (representing the user who completed the project).</p> <p>Often, <code>user_id</code> and <code>completer_id</code> will be the same (if the user who was assigned the project completes it). However, if another user completes it, user_id and completer_id will be different.</p> <p>In my User model, I have the following: </p> <pre><code>class User &lt; ActiveRecord::Base has_many :assignments has_many :incomplete_assignments, :class_name =&gt; 'Assignment', :conditions =&gt; 'completer_id IS NULL' has_many :completed_assignments, :class_name =&gt; 'Assignment', :foreign_key =&gt; 'completer_id' # this is the important one has_many :incomplete_projects, :through =&gt; :assignments, :source =&gt; :project, :conditions =&gt; 'completer_id IS NULL' end </code></pre> <p>I would like to make another association, called <code>:completed_projects</code>, which uses <code>completer_id</code> as the foreign key for the User in the <code>:through</code> model, rather than <code>:user_id</code>. Is it possible to do this?</p> <p>And, as an aside, I am aware of the <code>:foreign_key</code> option. However, this option is ignored when using <code>:through</code>, so I'd like to know if there's a way to do this without it.</p> <p>Finally, I should mention that I'm open to other designs, if it can't be done this way and someone can think of a better way. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. UShobodave
    1. USjakeboxer
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POSpecifying the foreign key in a has_many :through relationship
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POSpecifying the foreign key in a has_many :through relationship
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POSpecifying the foreign key in a has_many :through relationship
      1. This table or related slice is empty.
      1. VTUpMod
    1. COWelcome to trying to do something moderately complex with ActiveRecord. :)
      singulars
      1. POSpecifying the foreign key in a has_many :through relationship
      1. UShobodave
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload