USE NTU
GO
CREATE TRIGGER maak_bedrag_na_insert ON aankoop
AFTER INSERT
AS
BEGIN
 SET NOCOUNT ON;

   DECLARE
   @aankoop_nr INT,
   @aantal INT,
   @prijs money,
   ----------------------------------


    @aantalretour INT,
    @order_id INT,
    @product_id INT,
    @oudbedrag MONEY,
    @oudaantal INT,
    @retournummer INT;



   SELECT @aantalretour = inserted.aantal
   FROM inserted;

   SELECT @order_id = inserted.[ORDER]
   FROM inserted;

   SELECT @product_id = inserted.prod
   FROM inserted;

   SELECT @retournummer = inserted.retour
   FROM inserted;

   SELECT @oudbedrag = aankoop.bedrag
   FROM aankoop
   WHERE [ORDER] = @order_id AND aankoop.retour IS NULL;

   SELECT @oudaantal = aankoop.aantal
   FROM aankoop
   WHERE [ORDER] = @order_id AND aankoop.retour IS NULL;
   ----------------------------------------
    SELECT @aankoop_nr = inserted.aankoop_nr
    FROM inserted;

    SELECT @aantal = inserted.aantal
    FROM inserted;

    SELECT @prijs = prijs FROM
    product WHERE prod_nr = @product_id;
    -----------------------------------



   IF @retournummer IS NULL

    UPDATE aankoop
    SET bedrag = @prijs * @aantal
    WHERE aankoop_nr = @aankoop_nr;


   IF @retournummer IS NOT NULL
   IF @aantalretour>@oudaantal AND @aantalretour <0
   ROLLBACK TRANSACTION
   ELSE

   UPDATE aankoop
   SET bedrag = -(@oudbedrag / @oudaantal) * @aantalretour
   WHERE aankoop_nr = @aankoop_nr;

   UPDATE aankoop
   SET aantal = @aantalretour*-1
   WHERE  aankoop.[ORDER] = @order_id AND aankoop.retour = @retournummer;

END