Rails how to sum columns?

ruby-on-rails ruby ruby-on-rails-3 ruby-on-rails-3.1

You can summarize directly on the database by creating the respective SQL like this:

Pakke.sum(:prismd, :conditions => {:id => [4,5]})

On newer Rails versions (i.e. Rails >= 4.0), you can use an ActiveRecord queries more intuitively, such as:

Pakke.where(id: [4,5]).sum(:prismd)

See ActiveRecord::Calculations for more usage examples and general documentation.

ruby-on-rails ruby ruby-on-rails-3 ruby-on-rails-3.1

ActiveRecord has a bunch of built-in calculation methods, including sum:

@test = Pakke.where(:id => [4, 5] ).sum(:prismd)

ruby-on-rails ruby ruby-on-rails-3 ruby-on-rails-3.1

Pakke.find([[14], [15]]).map(&:prismd).sum

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