Oracle mutating tables - oracle

Question

I have this procedure which calculates the total amount paid for a car and determines if the car status can be changed to 'SOLD' if the amount is equal to the price.
I know the problem is the query in car_payment but I can't find other way to make the sum of the amount, can anybody help me, please?
create or replace trigger tr_paid_car
before insert
or update of amount
on car_payment
for each row
declare
v_amount number;
v_car_status_id car_status.car_status_id%type;
v_price car.price%type;
begin
select sum(amount)
into v_amount
from car_payment
where car_id = :new.car_id;
if inserting then
v_amount := v_amount + :new.amount;
elsif updating then
v_amount := v_amount + :new.amount - :old.amount;
end if;
select price
into v_price
from car
where car_id = :new.car_id;
if v_amount >= v_price then
select car_status_id
into v_car_status_id
from car_status
where description = 'SOLD';
update car
set car_status_id = v_car_status_id
where car_id = :new.car_id;
end if;
end;
/

Answer 1

Create a another function called: GET_CAR_PAY_AMT as below.
CREATE OR REPLACE FUNCTION GET_CAR_PAY_AMT(p_car_id car_payment.car_id%type) return number
as
pragma autonomous_transaction;
x number;
begin
select sum(amount)
into x
from car_payment
where car_id = p_car_id;
return x;
end GET_CAR_PAY_AMT;
Now use function GET_CAR_PAY_AMT instead of your SELECT statement in the trigger as below:
Replace below SQL:
select sum(amount)
into v_amount
from car_payment
where car_id = :new.car_id;
With:
v_amount := GET_CAR_PAY_AMT(:new.car_id);