Group and count in Rails

ruby-on-rails count
tladuke picture tladuke · Jan 7, 2010 · Viewed 62.2k times · Source

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 down: 

@line_items = @project.line_items.all(:group => "device_id")

This is for my line item index view, which is just a table displaying the line items. How do I make a column in that table for "count" now that the line items are grouped by device?

Answer

Chandra Patni picture Chandra Patni · Jan 7, 2010

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

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