Find duplicated users using Ruby

Question

I am having trouble finding a way to find from a single query if there are users duplicated in my database.

How could I query to find dupped users in Ruby using ActiveRecord?

The database structure is here: http://www.collectivestep.com/discoursedb/

Answer 1

Take an example like you want to find user that have same name and email then try this one and you will get all user that have same name and email and once you get this output delete those User,

User.find(:all, :group => :username, :having => "count(*) > 1" )

Answer 2

For MySql database you can try following query

User.find(:all, :group => [:username], :having => "count(*) > 1" )

For Postgres you can try following query

User.select(:username).group(:username).having("count(*) > 1")