SQL Trigger Error ORA-04098 - sql

Question

i have two tables named as childs and parent.
create table parent(
wallet_id NUMBER generated always as identity,
amount int,
customer_id int,
primary key(wallet_id),
Foreign key (customer_id) REFERENCES childs(customer_id)
);
create table childs(
customer_id number generated always as identity,
name varchar2 (255)
);
Now what i wanted to achieve was to get name from childs , and assign a wallet_id to childs in parent table as parent table has a foreign key to customer_id.
For this purpose i created a trigger.
create or replace
TRIGGER TRIGGER1
AFTER INSERT ON CHILDS
Declare
id int;
BEGIN
select MAX(customer_id) into id FROM childs;
insert into parent (customer_id ) values ( id );
END;
Now trigger is created but when i insert value in childs,
insert into childs(names) values ('jarral');
Now following error appears:
SQL Error: ORA-04098: trigger 'SYSTEM.TRG' is invalid and failed re-validation
04098. 00000 - "trigger '%s.%s' is invalid and failed re-validation"
*Cause: A trigger was attempted to be retrieved for execution and was
found to be invalid. This also means that compilation/authorization
failed for the trigger.
*Action: Options are to resolve the compilation/authorization errors,
disable the trigger, or drop the trigger.
How can i solve that?

Answer 1

I'm not entirely sure I follow your question, but is this what you are after ?
SQL> create table t1 ( id number generated as identity , x int);
Table created.
SQL> create table t2 ( id number generated as identity , t1_id int);
Table created.
SQL>
SQL> create or replace
2 trigger trg
3 after insert on t1
4 for each row
5 begin
6 insert into t2 (t1_id) values ( :new.id);
7 end;
8 /
Trigger created.
SQL> insert into t1 (x) values ( 0);
1 row created.
SQL> select * from t1;
ID X
---------- ----------
1 0
SQL> select * from t2;
ID T1_ID
---------- ----------
1 1