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# DBMS-specific queries with Rails

Have you ever wanted to run queries which are specific to the type of database you’re connected to in Rails? Well, here’s one way of doing it :

class Random < ActiveRecord::Base
  def do_stuff
    case connection.class
    when ActiveRecord::ConnectionAdapters::MysqlAdapter
      find( :all, :order => "RAND()" )
    when ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
      find( :all, :order => "RANDOM()" )
    else
      raise "Merrrrh." 
    end
  end
end

Is there a better way? Answers on a postcard …

Update : This broke in either Rails 2.0 or 2.1. Rails’ new behaviour is to only load the connection adapters you’re actually using, so you’ll need to do something like this instead :

if ActiveRecord::ConnectionAdapters.constants.include? MysqlAdapter
  ...
else ...
  ...
end