Ruby on Rails 4. How to write a query to group rows by date?

Question

Ruby on Rails

Hello. I can't write the right query to get this result (group records by day):

date(day) - sum(field1) - sum(field2)

The code that is:

@downloads = Download
.order(created_at: :desc)
.includes(:document)
.joins(:document)
.where('documents.uploaded_by = ?', params[:user_id])
.page(params[:page])

document has_many downloads
download belongs_to
document

Answer 1

The general principle is this:

Download
  .joins(:document)
  .where(documents: {uploaded_by: params[:user_id]})
  .group(:created_at)
  .pluck(:created_at, 'sum(поле1)', 'sum(поле2)')

Answer 2

There is such a useful gem for grouping by dates, but it won't do '-sum...' for you.
It seems to me that it's easier to write a query in pieces of SQL