limit the amount of trigger updates for a specific row in oracle - oracle

Question

I want to audit update changes in a specific table, and for that I've created a trigger that tracks every time a row is updated, it then write the updated changes into a new historical table:
create table test (id number generated always as identity,name varchar2(10) default null, school varchar2(10) null);
insert into test (name,school) values ('John','MIT');
insert into test (name,school) values ('Max','Oxford');
create table test_history (id int,name varchar2(10), school varchar2(10));
create or replace trigger test_trigger
after update
of name,school
on test
for each row
begin
insert into test_history
values
(
:old.id,
:new.name,
:new.school
);
end;
/
What I would like to do is to limit the amount a specific row is updated to a certain value. For example, the following update statement can only be executed 10 times:
update test
set
name = 'Jason'
where id = 1;
In this way if I execute the above statement 10 times it should work, but if the execution happens the 11th time it should fail. So the maximum amount of rows of a specific unique id is 10.

Answer 1

Count number of rows in the history table and raise an error if it exceeds value you find appropriate.
SQL> create or replace trigger test_trigger
2 after update
3 of name,school
4 on test
5 for each row
6 declare
7 l_cnt number;
8 begin
9 select count(*) into l_cnt
10 from test_history
11 where id = :new.id;
12
13 if l_cnt <= 10 then
14 insert into test_history
15 values
16 (
17 :old.id,
18 :new.name,
19 :new.school
20 );
21 else
22 raise_application_error(-20000, 'Too many updates');
23 end if;
24 end;
25 /
Trigger created.
Update:
SQL> update test set name = 'Jason' where id = 1;
1 row updated.
<snip>
SQL> update test set name = 'Jason' where id = 1;
1 row updated.
SQL> update test set name = 'Jason' where id = 1;
update test set name = 'Jason' where id = 1
*
ERROR at line 1:
ORA-20000: Too many updates
ORA-06512: at "SCOTT.TEST_TRIGGER", line 17
ORA-04088: error during execution of trigger 'SCOTT.TEST_TRIGGER'
SQL>