Table Goods_has_Taker(order_id,good_id...)
Table Goods (good_id, price...)
Table OrderD (order_id, transaction_date, amount)

CREATE DEFINER = CURRENT_USER TRIGGER `mydb`.`OrderD_BEFORE_INSERT`
       BEFORE INSERT ON `OrderD` FOR EACH ROW
BEGIN
  DECLARE quantity Int;
  declare price FLoat;

  set new.transaction_date=NOW(),
      @quantity :=
        (select out_quantity from Goods_has_Taker
         where Goods_has_Taker.order_id=new.order_id),
      @price :=
        (select price from  Goods
         Inner Join Goods_has_Taker
         On Goods.good_id=Goods_has_Taker.good_id
         Where new.order_id = Goods_has_Taker.order_id
        ),
      new.amount=@quantity*@price;
END