Ordering rows by a number of referencing records

rubyonrails-talk
1

Hello all,

There are 2 tables in a one-to-many relation. I want to order rows in the parent table according to the number of rows in the child table referencing the parent table.

In SQL I would do it the following way:

select service_partners.id, count(couriers.first_name) as courier_count   from service_partners   left join couriers on service_partners.id = couriers.service_partner_id   group by service_partners.id   order by courier_count;

Using ActiveRecord it is done by

ServicePartner.find(:all,    :select => 'service_partners.id, count(couriers.first_name) as cn ',    :joins => 'left join couriers on service_partners.id = couriers.service_partner_id',    :group => 'service_partners.id ',    :order => 'cn asc'

You might think why the guy is not using :include => :couriers instead of :joins. The answer is that using :include makes ActiveRecord ignore (and I can understand why) the :select argument which I need.

So my question is if anybody sees a more elegant way to do this?

Cheers, Yuri