If you want to load data from 2 tables (with a belongs_to/has_many relation)

rails-find-joins.rb

    metrics_with_inputs = Revision.find(
      :all,
      :conditions => { :id => self.revisions.map { |r| r.id } },
      :select => 'revisions.metric, revisions.snap_date, revisions.updated_at,
        inputs.author, inputs.as_of_date, inputs.units',
      :joins => 'join inputs on inputs.revision_id = revisions.id',
      :order => 'revisions.metric, revisions.snap_date, revisions.updated_at'
    )