如何在两个表上一个接一个地写入更新的触发器

Question

Customer(cid, cname, caddress, ccity, cstate, czip, ccardnum)
Product(pid, pname, pbrand, pprice)
ShoppingCart(cartid, cid, active, totalprice)          
ShoppingCart.cid references to Customer.cid
CartItem(cartid, pid, iprice, iquantity)     
CartItem.cartid references ShoppingCart.cartid, 
CartId.pid references Product.pid
Order(oid, cartid, time, payprice) Order.cartid references to ShoppingCart.cartid

Create triggers that, when the price of a certain product changes, update the price of this item in any active shopping cart containing the item, and also updates the total price of these shopping carts?.

CREATE TRIGGER priceupdate AFTER UPDATE ON product
FOR EACH ROW
BEGIN
UPDATE cartitem 
SET iprice=new.pprice 
WHERE pid=new.pid 
and cartid in 
(select cartid                                           
from shoppingcart WHERE active='1');

UPDATE shoppingcart 
SET totalprice = 
(select sum(iprice*iquantity) 
from cartitem WHERE cartid=new.cartid;
END;

Above code was givin me error because i am updating shopping cart which is used for updating cartitem
When I tried code given below worked fine but I am not able to update total price in shoppingcart.Can Someone help me with updating shopping cart totalprice

CREATE TRIGGER priceupdate AFTER UPDATE ON product
FOR EACH ROW
BEGIN
UPDATE cartitem 
SET iprice=new.pprice 
WHERE pid=new.pid and cartid in 
(select cartid                                           
from shoppingcart WHERE active='1');
END;

NOTE:I am using MYSQL

Sample data: http://www.sqlfiddle.com/#!2/8489e9/4/3

Answer 1

Try

DELIMITER $$
CREATE TRIGGER product_priceupdate 
AFTER UPDATE ON product
FOR EACH ROW
BEGIN
  UPDATE cartitem i JOIN shoppingcart c
      ON i.cartid = c.cartid
     SET i.iprice = NEW.pprice 
   WHERE i.pid = NEW.pid 
     AND c.active  = 1;

  UPDATE shoppingcart c JOIN
 (
   SELECT cartid, SUM(iprice * iquantity) totalprice
     FROM cartitem 
    WHERE cartid IN
          (
            SELECT DISTINCT i.cartid 
              FROM cartitem i JOIN shoppingcart c
                ON i.cartid = c.cartid
             WHERE i.pid = NEW.pid 
               AND c.active  = 1
          )
    GROUP BY cartid
 ) q
     ON c.cartid = q.cartid
    SET c.totalprice = q.totalprice;
END$$
DELIMITER ;

Here is SQLFiddle demo