From: Todd Benson <caduceass@...>
Date: 2008-08-13T01:47:39+09:00
Subject: Re: store data in join table

On Tue, Aug 12, 2008 at 6:00 AM, Ganesh Kumar <gani_chinta@yahoo.com> wrote:
> Hi,
>  I have one join table called
>
>  for example "students_subjects" and i am having relationship like
> in
> student model
> :has_many=>subjects ,:through=>students_departments
>
> in
> subjects table
> :has_many=>students ,:through=>students_departments
>
> i need to store data in join table
> join table columns
>
> 'id' 'student_id' 'subject_id'
>
> how can i store plz reply if anybody knows solution.....

I don't know why people pick those type of names for tables, but a
similar schema is...

create table people (
  account varchar not null primary key
);

create table collection (
  team varchar not null primary key
);

create table membership (
  account varchar not null references people (account),
  team varchar not null references collection (team),
  primary key (account, team)
);


You'd want to add check constraints in a real database, along with
other info, of course.

I'm pretty sure ActiveRecord will force you to use an arbitrary ID
field with the join table.  I haven't used ActiveRecord in a while,
but IIRC, I think I circumvented that annoyance by using "unique"
instead of "primary key" for my multiple keys in join tables.  The
ActiveRecord::Base class does allow you to define your own primary
keys (unless they're multiple).

hth,
Todd