Rails find record with zero has_many records associated [duplicate]

Answer 1

When trying to find records with no matching records from the joined table, you need to use a LEFT OUTER JOIN

scope :with_photos, joins('LEFT OUTER JOIN photos ON cities.id = photos.city_id').group('cities.id').having('count(photos.id) > 0')
scope :without_photos, joins('LEFT OUTER JOIN photos ON cities.id = photos.city_id').group('cities.id').having('count(photos.id) = 0')