I've been confused for a while, I follow the [rails doc](http://guides.rubyonrails.org/active_record_querying.html#selecting-specific-fields), and it say 

`Client.select("viewable_by, locked")` will only select only a subset of fields. 

Now I got a model call `Goods`

```
class Goods < ActiveRecord::Base {
               :id => :integer,
             :name => :string,
    :translate_key => :string,
       :created_at => :datetime,
       :updated_at => :datetime,
    :discount_json => :text,
    :price_mapping => :text,
       :goods_type => :string,
     :reference_id => :integer,
        :available => :boolean
}

```

When I try `Goods.select(:name)`, it works fine.
However, when I did 

```
Goods.select(:name,:translate_key)

```

It threw `ArgumentError: wrong number of arguments (2 for 0..1)`