다음 절차를 대신 트리거로 변경할 수 있습니까?

Question

CREATE or REPLACE PROCEDURE UPDATE_SUBTOTAL is 

v_order_no orderline.order_no%type; 

v_subtotal number(15); 

CURSOR product_orderline_cur is 

SELECT ol.order_no, sum(p.unit_price * ol.qty) as subtotal 

from product p, orderline ol 

where p.product_no = ol.product_no 

group by ol.order_no; 

BEGIN 

OPEN product_orderline_cur; 

LOOP 

    FETCH product_orderline_cur into v_order_no, v_subtotal; 

    EXIT when product_orderline_cur%notfound; 

    -- store subtotal in orders table 

    UPDATE orders 

    SET subtotal = v_subtotal 

    WHERE order_no = v_order_no; 

END LOOP; 

--an order may be created but no orderlines added yet,insert a 0 

UPDATE orders 

SET subtotal = 0 

WHERE subtotal is null; 

CLOSE product_orderline_cur; 

END; 

/
show errors; 

Answer 1

CREATE OR REPLACE TRIGGER orders_before_update 
BEFORE UPDATE ON orders 
    FOR EACH ROW 

DECLARE v_sum INT; 

BEGIN 

    SELECT SUM(p.unit_price * ol.qty) 
    INTO v_sum 
    FROM product p INNER JOIN orderline ol 
     ON p.product_no = ol.product_no 
    WHERE ol.order_no = :new.order_no; 

    :new.subtotal := COALESCE(v_sum, 0); 
END;