scope creating array rather than activerecord::relation

gistfile1.rb

  scope :for_account, lambda { |account| 
    find_by_sql("SELECT 'tickets'.* FROM 'tickets' 
      INNER JOIN 'groups' ON 'groups'.'id' = 'tickets'.'group_id' 
      INNER JOIN 'assignments' ON 'groups'.'id' = 'assignments'.'group_id' 
      INNER JOIN 'accounts' ON 'accounts'.'id' = 'assignments'.'account_id' 
        WHERE ('accounts'.'id' = #{account.id})
    UNION
    SELECT 'tickets'.* FROM 'tickets' 
      INNER JOIN 'tasks' ON 'tasks'.'ticket_id' = 'tickets'.'id' 
      INNER JOIN 'accounts' ON 'accounts'.'id' = 'tasks'.'account_id' 
        WHERE ('accounts'.'id' = #{account.id})") }