rails 3 group by date a datetime column
This should work (rails 3):
Foo.order(:start_at).group("DATE(start_at)").count
edit: if you're using PostgreSQL, the query should be
Foo.order("DATE(start_at)").group("DATE(start_at)").count
or you'll get an error
("PGError: ERROR: column "foos.start_at" must appear in the GROUP BY clause or be used in an aggregate function")
Based on
Graphing new users by date in a Rails app using Seer
and
http://www.pastbedti.me/2009/11/grouping-a-timestamp-field-by-date-in-ruby-on-rails-postgresql/
I created a gem for this. https://github.com/ankane/groupdate
Foo.group_by_day(:created_at).count
You can even specify a time zone.
Foo.group_by_day(:created_at, time_zone: "Pacific Time (US & Canada)").count