ruby - Rails how to sum columns?

Question

Example I have:

@test = Pakke.find([[4], [5]])

In my Pakke table I have a column named prismd

How do I sum the two values for the prismd columns for @test?

Answer 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.