Group and count in Rails

Question

I know I\'ve seen this before but I can\'t find anything now. I want to group a query by a certain column and be able to display how many are in each group. I got the first part

Answer 1

something like

 User.all(:joins => :comments, :select => "users.*, count(comments.id) as comments_count", :group => "users.id")

might also work...

Answer 2

I think you can try this as well.

@project.line_items.group(:device_id).pluck("device_id, count(device_id)")

^^ This gives array of arrays with elements 'device_id and count'

Answer 3

hash of devise_id as key and associated records count

@project.line_items.group(:device_id).count

Answer 4

Just add a :select option:

@line_items = @project.line_items.all(
  :group  => "device_id",
  :select => "device_id, COUNT(*) as count"
)

Then each @line_item will have a count attribute.

Answer 5

You can do count on line_items which will return you an ordered hash of device_id and count.

@project.line_items.group(:device_id).count

Answer 6

For only count pluck would be faster here rather than group

@project.line_items.pluck(:device_id).count


@project.line_items.pluck(:device_id).uniq.count