Why do I keep getting Error 1172 in this MySQL trigger? - mysql

Question

What I'm trying to do is this:
Create a trigger named trg_cust_balance that will automatically update the AC_CUSTOMER table’s CUS_BALANCE before a new CHARTER row is added. Use the CHARTER table’s CHAR_TOT_CHG as the update source (Assume that all charter charges are charged to the customer balance.) In addition to the CHAR_TOT_CHG, add $25 for every quart of oil used on the charter.
This is my code:
create trigger trg_cust_balance
before insert on CHARTER
for each row
begin
declare CHG_PRIOR double;
declare OIL_QUANT double;
select CHAR_OIL_QTS into OIL_QUANT
from CHARTER
order by CUS_CODE;
select CHAR_TOT_CHG into CHG_PRIOR
from CHARTER
order by CUS_CODE;
update AC_CUSTOMER
set CUS_BALANCE = CUS_BALANCE + CHG_PRIOR + (OIL_QUANT * 25);
end;
// delimiter ;
So basically what I'm doing here is pulling the quantity of quarts of oil (CHAR_OIL_QTS) and the total charge (CHAR_TOT_CHG) and turning them into variables. Then trying to make the customer balance (CUS_BALANCE) equal to whatever it was plus said charges. However, I keep getting the 1172 error and I don't know why. I suspect it's got to do with the two select statements. Any help would be appreciated, thanks

Answer 1

And you can reduce it to following
But the update clause needs an other WHERE Clause so that the correct custimer gets the balanced changed
drop trigger if exists trg_cust_balance;
delimiter //
create trigger trg_cust_balance
before insert on CHARTER
for each row
begin
update AC_CUSTOMER
set CUS_BALANCE = CUS_BALANCE + NEW.CHAR_TOT_CHG + (NEW.CHAR_OIL_QTS * 25)
where AC_CUSTOMER.CUS_CODE = NEW.CUS_CODE;
end//
delimiter ;
INSERT INTO CHARTER VALUES(10019,'2020-02-10','4278Y','TYS',644,3.8,4.5,167.4,0,10017);
Thsi runs with out a proem seee https://www.db-fiddle.com/f/29eiHwfNHDrL34VQ8CSPAF/1