trigger to delete from two tables simultaneously in sql oracle apex - sql

Question

I have two tables: teachers and advisers, which have some repeating values(a person can be both teacher and adviser)
teacher has primary key: Teachers_id, which is foreign key in advisers table
I want to make a trigger that would delete values from adviser, if they were deleted in teacher
I tried to do it like this, but I have a mistake, which I cannot find
create or replace TRIGGER delete_teacher
AFTER
DELETE on TEACHER
FOR EACH ROW
declare
pragma autonomous_transaction;
BEGIN
DELETE FROM ADVISER
WHERE ADVISER.T_id = TEACHER.T_id;
END;
I'm working in oracle apex

Answer 1

That's
CREATE OR REPLACE TRIGGER delete_teacher
AFTER DELETE
ON teacher
FOR EACH ROW
BEGIN
DELETE FROM adviser where t_id = :old.t_id;
END;
trigger doesn't have to be (and shouldn't be) an autonomous transaction (why do you think it should be?)
reference deleted row with its :old pseudorecord
On the other hand, if you created the foreign key constraint so that it deletes child records automatically, you wouldn't have to create any triggers.
SQL> create table teacher
2 (t_id number primary key,
3 name varchar2(10));
Table created.
SQL> create table adviser
2 (a_id number primary key,
3 t_id number references teacher on delete cascade, --> this
4 name varchar2(10));
Table created.
Sample rows:
SQL> insert all
2 into teacher values (1, 'Little')
3 into teacher values (2, 'Foot')
4 into adviser values (100, 1, 'Little')
5 select * from dual;
3 rows created.
Delete teacher whose t_id = 1; Oracle will delete both master and detail records:
SQL> delete from teacher where t_id = 1;
1 row deleted.
SQL> select * from teacher;
T_ID NAME
---------- ----------
2 Foot
SQL> select * from adviser;
no rows selected --> see? No Little here.
SQL>