Problem with FETCH

Question

If you have a fetch statement inside of a LOOP like below, should it fetch the NEXTVAL or have I missed something?
When I run this I get a unique constraint violated (order_id is PK)
declare
cursor next_order_id is select seq_order_id.nextval from dual;
v_order_id number;
over_30_rec over_30_cur%ROWTYPE;
begin
IF NOT next_order_id%ISOPEN THEN
     OPEN next_order_id;
END IF;
FOR over_30_rec IN over_30_cur
     LOOP     
          FETCH next_order_id INTO v_order_id;
          INSERT INTO ord_detail (order_id,
               customer_id,
                    action_id,
               action_date,
               call_length,
               employee_id)
     VALUES (V_order_id,
     over_30_rec.customer_id,
     '15',
     sysdate,
     null,
     '7');
     END LOOP;
close next_order_id;
end;

Answer 1

Because you are leaving the cursor open for the duration of the loop, you will end up fetching the same value over and over again - thus the PK constraint violation.
Actually, I would recommend NOT using a cursor for your sequence management. My first choice would be to handle it via a trigger, but if it needs to actually appear in your insert statement then:
FOR over_30_rec IN over_30_cur LOOP
  INSERT INTO ord_detail
    (order_id, customer_id, action_id, action_date, call_length, employee_id)
   VALUES (seq_order_id.nextval, over_30_rec.customer_id, '15',
sysdate, null, '7');
END LOOP;And on a second pass, unless you are doing something in your loop that you didn't show in your example, you can do this insert in one statement (no loop):
insert into ord_detail
  (order_id, customer_id, action_id, action_date, employee_id)
  select seq_order_id.nextval, customer_id, '15', sysdate, '7'
    from join_making_up_over_30_cur;Anything you can do in a single statement is generally preferrable to a procedural approach.