pluck and select

• pluck return Array object as the result
• select return ActiveRecord::Relation object as the result
• select always returns id: nil property in your ActiveRecord results if you don't select :id. For converting your object to json without id:nil, you could do as following: record(s).to_json(only:[:column1, :column2, ...:column3])

  photos = Photo.select(:name, :path_original, :path_small)
  respond_with photos.to_json(only: [:name, :path_original, :path_small])
  

Reference

• Getting to Know Pluck and Select
• rails joins with select returns nil as id