Redmine

  [...]

  # Versions are sorted by effective_date and name
  # Those with no effective_date are at the end, sorted by name
  def <=>(version)
    if self.effective_date
      if version.effective_date
        if self.effective_date == version.effective_date
          name == version.name ? id <=> version.id : name <=> version.name
        else
          self.effective_date <=> version.effective_date
        end
      else
        -1
      end
    else
      if version.effective_date
        1
      else
        name == version.name ? id <=> version.id : name <=> version.name
      end
    end
  end

  def self.fields_for_order_statement(table=nil)
    table ||= table_name
    ["(CASE WHEN #{table}.effective_date IS NULL THEN 1 ELSE 0 END)", "#{table}.effective_date", "#{table}.name", "#{table}.id"]
  end

  scope :sorted, order(fields_for_order_statement)

  [...]