sql - Trigger to sum value of column of all rows and store in a column

Question

I have two tables in oracle.

invoice(id_invoice, description, price)

product_invoice(id,id_invoice, description, price, quantity, final_price)

I want to do the the "sum" of the column of "final_price" with all the rows with the same "id_invoice" and store it in the table invoice. I'm trying using triggers but not working. Here's my trigger

create or replace NONEDITIONABLE TRIGGER updateukupno AFTER insert ON stavkaotpremnice FOR EACH ROW BEGIN
UPDATE invoice a
SET a.price = 
    (SELECT SUM(final_price) 
       FROM product_invoice
      WHERE id_invoice = a.id_invoice)
 WHERE a.id_invoice = :NEW.id_invoice;
END;

Answer 1

I think this type of logic is usually expressed incrementally:

UPDATE invoice i
    SET price = price + coalesce(:new.final_price, 0)) 
    WHERE i.id_invoice = :NEW.id_invoice;