What I want to do:
get all users that not belong to the declaration.
I could do a loop. First get all the users. I know who belong to the
declaration, so I also know who does not.
But this seems like a lot of looping.
Is there an easy way I can get all those users that NOT belong to the
declaration? I looked into using joins in my find, but I don’t know how
to use that in this context.
Leon, I think a left outer join of Users on Declarations would do
it.
in SQL that would be:
SELECT * from Users left outer join Declarations ON Users.user_id =
Declarations.user_id WHERE Declarations.user_id IS NULL
in ActiveRecord, an :includes does a left outer join so (I may not get
this 100% right)
User.find(:all, :conditions => “declarations.user_id is
NULL”, :include => “declarations”)