Question

I’m trying to count the number of rows with a distinct column with Active Record.

The following SQL works and gives me the correct result:

SELECT COUNT(DISTINCT(user_id)) FROM attempts WHERE score = 100 AND problem_id = 1

But this code throws an ActiveRecord::StatementInvalid error:

attempts.where(:score => 100).count(:distinct => :user_id)

Answer 1

Try:

attempts.count('user_id', :conditions => "score = 100", :distinct => true)

more infos: http://ar.rubyonrails.org/classes/ActiveRecord/Calculations/ClassMethods.html