Whats the Rails way to do a query for the latest lesson_plan record for each user_id?

class LessonPlan < ActiveRecord::Base
    belongs_to :user
end

All the posts I've seen include joins or subqueries. Isn't there a simple way to do this?

I've tried

LessonPlan.select(['distinct(user_id)', :id, :created_at]).where(:user_id => users).order('created_at DESC') 

Which produces a query like.

SELECT distinct(user_id), id, created_at FROM `lesson_plans` WHERE `lesson_plans`.`user_id` IN (110031, 110032, 110033, 110034) ORDER BY created_at DESC

But when I try this query, it returns rows with duplicate user_id's.

Sorry if this is a duplicate question, I've really looked around for a solution.

• ruby-on-rails
• activerecord
• distinct

Rails#ActiveRecord:

LessonPlan.select([:user_id, :id, 'MAX(created_at)']).group(:user_id).limit(10)

MySql :

select id, user_id, MAX(created_at) from lesson_plans group by user_id limit 10

May be its work

LessonPlan.select([:user_id, :id, 'MAX(created_at)']).group(:user_id)