How can I count the number of records that have a unique value in a particular field in ROR?
Solution 1:
This has changed slightly in rails 4 and above :distinct => true is now deprecated. Use:
Record.distinct.count('date')
Or if you want the date and the number:
Record.group(:date).distinct.count(:date)
Solution 2:
What you're going for is the following SQL:
SELECT COUNT(DISTINCT date) FROM records
ActiveRecord has this built in:
Record.count('date', :distinct => true)
Solution 3:
Outside of SQL:
Record.find(:all).group_by(&:date).count
ActiveSupport's Enumerable#group_by is indispensable.