How to find records that have duplicate data using Active Record

Question

What is the best way to find records with duplicate values in a column using ruby and the new Activerecord?

Answer 1

In Rails 2.x, select is a private method of AR class. Just use find():

klass.find(:all, 
  :select => "id, count(the_col) as num", 
  :conditions => ["extra conditions here"], 
  :group => 'the_col', 
  :having => "num > 1")