Rails merge 2 query results - ruby-on-rails

Question

I want to show first users with last_request >= 1.day.ago and then add the rest users
def self.default_scope
where("last_request >= ?", 1.day.ago) + where("last_request < ? OR last_request is null", 1.day.ago)
end
This code raises that error:
undefined method `merge' for []:Array
How could I do that?
UPDATE
Error stack
NoMethodError - undefined method `merge' for #<Array:0xd16ba90>:
activerecord (3.2.13) lib/active_record/relation.rb:503:in `with_default_scope'
activerecord (3.2.13) lib/active_record/relation.rb:167:in `exec_queries'
activerecord (3.2.13) lib/active_record/relation.rb:160:in `block in to_a'
activerecord (3.2.13) lib/active_record/explain.rb:34:in `logging_query_plan'
activerecord (3.2.13) lib/active_record/relation.rb:159:in `to_a'
will_paginate (3.0.5) lib/will_paginate/active_record.rb:127:in `block in to_a'
will_paginate (3.0.5) lib/will_paginate/collection.rb:96:in `create'
will_paginate (3.0.5) lib/will_paginate/active_record.rb:126:in `to_a'
UPDATE2
I am using rails_admin, datetime field ordering is not working correctly
1)Order by ascending
2)Order by descending

Answer 1

In your particular case you can combine scopes to one with
default_scope where('last_request >= :time OR (last_request < :time OR last_request IS NULL)', time: 1.day.ago).order('last_request DESC')
UPD
That is not ActiveRecord or RailsAdmin issue, more info
ORDER BY ASC with Nulls at the Bottom
Rails: Order with nulls last