Question

I’m new to Oracle and SQL and I’m trying to create a trigger where the req_ship_date (suborder table) cannot be before the order_date (customer_order table). I created the trigger:

create or replace trigger req_ship_date_error
before insert on suborder
for each row
declare
placed_date date;
req_date date;
begin
select order_date into placed_date
from customer_order;
select req_ship_date into req_date
from suborder
where suborder_no = :new.suborder_no;
if placed_date > req_date then
raise_application_error(-20002, ('Order ' || :new.suborder_no || ' required shipping date cannot be before order date'));
end if;
end;

But even after a try inserting a good statement I’m getting the following error

insert into suborder
values  ( 8, 2, '10-jul-2012', '12-jul-2012', 'CVS', 2);

ERROR

    Error starting at line 1 in command:
insert into suborder
    values  ( 8, 2, '10-jul-2012', '12-jul-2012', 'CVS', 2)
Error report:
SQL Error: ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at "COMPANY.REQ_SHIP_DATE_ERROR", line 5
ORA-04088: error during execution of trigger 'COMPANY.REQ_SHIP_DATE_ERROR'
01422. 00000 -  "exact fetch returns more than requested number of rows"
*Cause:    The number specified in exact fetch is less than the rows returned.
*Action:   Rewrite the query or change number of rows requested

Any idea what is causing this? Thanks

Answer 1

• As @Shine points out, you need to have a WHERE clause on the query against CUSTOMER_ORDER
• A row-level trigger on SUBORDER cannot then query SUBORDER. If you do that, you’ll end up getting a mutating table error in general. Assuming that SUBORDER_NO is the primary key of SUBORDER, however, you shouldn’t need to query the table. Simply use the :new.req_ship_date value you have in your hand.

Something like this should work assuming that the primary key of customer_order is order_no and that order_no exists in the suborder table.

create or replace trigger req_ship_date_error
  before insert on suborder
  for each row
declare
  l_placed_date date;
begin
  select order_date 
    into l_placed_date
    from customer_order
   where order_no = :new.order_no;
  if l_placed_date > :new.req_ship_date 
  then
    raise_application_error(
      -20002, 
      'Order ' || :new.suborder_no || ' required shipping date cannot be before order date');
  end if;
end;