SQL procedure called from trigger - sql

Question

In Oracle environment (SQLPLUS I used). My question is how to alter the data of a newly inserted tuple.
Here is an example: I need to make sure whenever an insert happen to table "Orders", if its attribute "weight" is bigger than 100, its another attribute "size_level" must be 1. Otherwise (weight<=100), size_level must be 0.
In order to do this, I figured that I need to call a stored procedure.
CREATE OR REPLACE TRIGGER new_ship_trigger
AFTER INSERT ON Orders
FOR EACH ROW
BEGIN ATOMIC
CALL UpdateShipSizeLevel(:new)
END;
/
How should I write the code for the stored procedure part? Or maybe I need a cursor?
I am required NOT to add a constraint to table "Orders" and I should use no more than one trigger.

Answer 1

Here you'll find yet another Oracle trigger example. Also be sure to read e.g. PL/SQL Triggers.
create table so54b (
id number
,weight number
,weight_level number
);
create or replace trigger so54b_trg
-- note the trigger is also run in update
before insert or update on so54b
for each row
begin
-- you don't need to implement the trigger logic in a separate
-- subroutine. however sometimes it might make sense.
:new.weight_level :=
case
when :new.weight > 100 then 1
else 0
end;
end;
/
show errors
insert into so54b(id, weight) values (1, 99);
insert into so54b(id, weight) values (2, 100);
-- weight_level is overwritten by the trigger
insert into so54b(id, weight, weight_level) values (3, 101, 13);
select * from so54b order by id;
ID WEIGHT WEIGHT_LEVEL
---------- ---------- ------------
1 99 0
2 100 0
3 101 1
update so54b set weight = 80 where weight > 100;
select * from so54b order by id;
ID WEIGHT WEIGHT_LEVEL
---------- ---------- ------------
1 99 0
2 100 0
3 80 0