Rails Join Query For Empty Right Tables
Say you wanted to select all the accounts from your applications with no associated users. You’d think this would be obvious, however I racked my brain for a few minutes thinking of a Rails-way of sorting this out.
The good news is with Rails 2.2 or later, it can be accomplished like this thanks to join hashes.
Company.find(:all, :include => :users,
:conditions => { :users => { :id => nil } })
Before Rails 2.2, you would have had to resort to the following.
Company.find(:all, :include => :users,
:conditions => "users.id IS NULL")
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Thanks for that. I’ve used this to end on the getter methods on my Size model:
class Size :variants, :conditions => { :variants => { :size_id => self.id } })
end
end