Rails how to randomly pick a row in a table?

Question

How do I random pick a row in a table?

Example my table:

name   age 
Lars   24
Grete  56
Hans   56

I want to random pick a name.

Example:

@randomname = Model.where(:name 'Random')

And how do I only pick 1 random name each day. That I can use as a instant variable in view.

Are you picking a random column or row? This is slightly confusing... — Jakub Hampl, Mar 10 '11 at 18:42
Seems then that all the answers are trying to do random rows. — Jakub Hampl, Mar 10 '11 at 18:53
FYI, Rails beginner, columns are `name`, `age` and rows are `lars, grete, hans...` so your data has 2 columns and 3 rows. If you want random column, then you will get back text `name` or `age`, NOT it's *values*. — Zabba, Mar 10 '11 at 19:07
In that case you have a duplicate: http://stackoverflow.com/questions/3641057/rails-select-random-record or http://stackoverflow.com/questions/2752231/random-record-in-activerecord. — Jakub Hampl, Mar 10 '11 at 22:09

score 4 · Accepted Answer · answered Mar 10 '11 at 18:43

4

@randomname = Model.order('rand()').limit(1).first.name

answered Mar 10 '11 at 18:43

Kalendae

2,256
1
21
23

How do I create a random for a day. So it dos not create a random name each time I reload my browser – Rails beginner Mar 10 '11 at 18:45
4

`Model.order('rand()').first.name` will be enough. Limit 1 will be set automatically – fl00r Mar 10 '11 at 19:14

score 3 · Answer 2 · answered Mar 10 '11 at 18:58

3

A random column in Rails 3 is simply:

Model.columns.sample.name

answered Mar 10 '11 at 18:58

Jakub Hampl

39,863
10
77
106

2

This is the winning ticket. I'm unsure of why he would need a random column though... – maček Mar 10 '11 at 19:10

score 1 · Answer 3 · answered Mar 10 '11 at 19:17

If you want to get random object 1 per day, so you should store it somewhere. You can store it:

in separate file
in separate model
in the same model add rndm field

Lets implement the last one. It is quite easy. Imagine, that your Model called User. First, let's add new date field rndm:

rails g migration add_rndm_to_user rndm:date
rake db:migrate

Now we need to add some methods to your User model

class User < ActiveRecord::Base
  def self.random
    rndm = find_by_rndm Date.today
    unless rndm
      update_all :rndm => nil
      rndm = self.order('rand()').first
      rndm.update_attribute :rndm, Date.today
    end
    rndm
  end
end

so now you can call User.random from your controller

score 0 · Answer 4 · answered Mar 10 '11 at 18:41

I have some Rails 2 code that shows the idea i think, and it's very easy to convert to rails 3 :

random_monsters = self.find(:all, :conditions=>["level > 0 and level < ? and monster_type='monster'", user_level+2])
random_monster = random_monsters[rand(random_monsters.length)]

I've also seen somebody in SO propose an offset way like :

offset = rand(Model.count)
rand_record = Model.first(:offset => offset)

Rails how to randomly pick a row in a table?

4 Answers4