Retrieving Random Elements from an ActiveRecord « Mike Burns, Coder

Retrieving Random Elements from an ActiveRecord

This one is short but not something I immediately thought of. It doesn’t rely on an ActiveRecord abstraction, but I originally thought it would need to, so the title is to save future Web searchers.

The idea is that you want to create a list of all the Users, but ordered randomly. It turns out that it’s just this (Postgre)SQL:

SELECT * FROM users ORDER BY random();

So, in Rails:

User.find(:all, :order => 'random()')

Update: Check out the plugin based on this, and the drawbacks to this.

This entry was written by Mike Burns and posted on August 18, 2006 at 3:27 pm and filed under ruby with tags activerecord, rails, random, sql. Bookmark the permalink. Follow any comments here with the RSS feed for this post. Post a comment or leave a trackback: Trackback URL.

2 Comments

Gudata

Posted April 17, 2007 at 4:25 pm | Permalink

for mysql

User.find(:all, :order => ‘rand()’)

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Robert Nasiadek

Posted December 14, 2007 at 10:35 am | Permalink

Hello,

your method is very good if you want to select all the rows from the table in random order.
It wouldn’t do very good if you wanted to get just 1 row or even 10 out of 10000.
Here’s a nice way to get just 1 random row:

http://robzon.aenima.pl/2007/12/selecting-random-row-from-table.html

cheers!

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