On Monday, March 2, 2015 at 12:18:48 PM UTC-8, Andrew Burleson wrote:
>
> Sorry to ask a sort of newbie SQL question but I'm having a hard time
> remembering how to do this and translating it into Sequel:
>
> If I have to models like this:
>
> class Apartment < Sequel::Model
> one_to_many :residents
> end
>
>
> class Resident < Sequel::Model
> many_to_one :apartment
> end
>
>
>
> How can I query all apartments ordered by resident count? I thought that
> this might work...
>
> result = Apartment.eager_graph(:residents).order(:residents__count).all
>
>
> ...but that fails with a PG grouping error: "Sequel::DatabaseError:
> PG::GroupingError: ERROR: column "apartments.id" must appear in the
> GROUP BY clause or be used in an aggregate function..."
>
> Thanks for the help!
>
Simplest way is probably using a subselect in the order clause:
Apartment.order(Resident.where(:apartment_id=>:apartments__id).select{count{}.*})
Thanks,
Jeremy
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