How can I count the number of records that have a unique value in a particular field in ROR?

Question

I have a record set that includes a date field, and want to determine how many unique dates are represented in the record set.

Something like:

Record         


        

Answer 1

Outside of SQL:

Record.find(:all).group_by(&:date).count

ActiveSupport's Enumerable#group_by is indispensable.