Trigger Query

Question

Hi All,
I need help with the below scenario.
My requirement is to create an insert and update trigger on table say 'product_config'. Insert trigger works as expected but there is some issue with delete trigger.
Insert trigger will check if the product_id is already present in the setup table. If yes, then it will not do anything else it will insert the product_id and sub_prod_id in the setup table.(This way there will always be unique records in setup table)
In product_config table, there can be same product_ids with different seq number as illustrated below.
Delete trigger will check if the product_id of the row which is being deleted is there in any other row in product_config table. If yes, no data is deleted from setup else delete the product_id/sub_prod_id from setup.
Sample Data:
create table product_config(seq number not null,product_id char(5) not null,sub_prod_id varchar2(5));
alter table product_config add constraint pk_product primary key(seq);
create table setup (product_id varchar2(5) not null);
alter table setup add constraint pk_product1 primary key(product_id);
create or replace trigger insert_trigger
after insert on product_config
for each row
declare
v_count number:=0;
begin
select count(*) into v_count from setup where product_id=:new.product_id;
if v_count=0 then
insert into setup values(:new.product_id);
end if;
select count(*) into v_count from setup where product_id=:new.sub_prod_id;
if v_count=0 then
insert into setup values(:new.sub_prod_id);
end if;
end;
create or replace trigger delete_trigger
after delete on product_config
for each row
declare
v_count number:=0;
PRAGMA AUTONOMOUS_TRANSACTION;
begin
select count(*) into v_count from setup s,product_config p where s.product_id=p.product_id and p.product_id=:old.product_id;
if v_count=0 then
delete from setup where product_id=:old.product_id;
end if;
select count(*) into v_count from setup s,product_config p where s.product_id=p.product_id and p.product_id=:old.sub_prod_id;
if v_count=0 then
delete from setup where product_id=:old.sub_prod_id;
end if;
commit;
end;
insert into product_config values(1,'12345','ABC');
insert into product_config values(2,'12345','BCD');
insert into product_config values(3,'12345','CDE');
insert into product_config values(4,'12345','DEF');
commit;
Once the above insert statements are executed, insert_trigger fires and data in setup table is as below
select * from setup;
12345
ABC
BCD
CDE
DEF
Now when I try to delete the rows one by one.'12345' is not getting deleted frm setup table.
Example:
delete from product_config where seq=1;---ABC gets deleted... FINE
delete from product_config where seq=2;---BCD gets deleted... FINE
delete from product_config where seq=3;---CDE gets deleted... FINE
delete from product_config where seq=4;---DEF gets deleted... FINE BUT 12345 should also get deleted as there is no other record of this product_id which is present in product_config.
Please advice.
Thanks
Dave

Answer 1

>
delete from product_config where seq=4;---DEF gets deleted... FINE BUT 12345 should also get deleted as there is no other record of this product_id which is present in product_config.
>
No - it should not get deleted by your code since there IS a record for DEF when your code checks.
>
select count(*) into v_count from setup s,product_config p where s.product_id=p.product_id and p.product_id=:old.product_id;
if v_count=0 then
delete from setup where product_id=:old.product_id;
end if;
>
The above code attempts to delete the PARENT record. The next code will delete the CHILD record.
So for the last delete of DEF the code determines that there IS still a child record DEF for parent 12345 and does not delete the parent.
Then your code deletes the CHILD record for DEF leaving the parent without any children.
You need to delete the children first - then if there are no children left delete the parent.
The use of an AUTONOMOUS transaction will also cause problems. If you do a DELETE of a record but then ROLLBACK that delete the trigger will still execute and delete the child and maybe the parent anyway.
NEVER perform non-transactional operations in a trigger. NEVER.
See my reply Posted: Mar 20, 2012 7:37 PM in this recent thread and be sure to read the last reply by an expert whose name you will recognize
Re: Procedure calling Inside a trigger
>
repetition is the key to success.
repetition is the key to success.
did I mention:
NEVER do anything non-transactional in a trigger (with the glaring exception of an autonomous transaction used to log and error message in a table - that is the ONLY valid use of autonomous transaction in any context I've ever seen - an error logging routine)
The original poster should
a) probably not use a trigger
b) definitely not use an autonomous transaction