Can %NOTFOUND return null after a fetch?

Question

This question raised a very interesting point; there seems to be a contradiction in the Oracle documentation on whether it\'s possible for %NOTFOUND to be null

Answer 1

I think the part that's tripping you up is this:

If FETCH never executes successfully, the EXIT WHEN condition is never TRUE and the loop is never exited.

Somewhere in the past there must have been a code example which looked like this:

LOOP
  FETCH c1 INTO name;
  EXIT WHEN c1%NOTFOUND;
  -- Do stuff
END LOOP;

Given this chunk of code, then the statement rings true. If the fetch never executes (fails), then %NOTFOUND will be null. The EXIT WHEN condition will not evaluate to TRUE (null evaluates to false). Then, indeed, the loop will continue forever.

Answer 2

This is a situation that is easily tested:

SET SERVEROUT ON;

DECLARE
  -- this cursor returns a single row
  CURSOR c1 IS
    SELECT 1 FROM dual WHERE rownum = 1;

  -- this cursor returns no rows
  CURSOR c2 IS
    SELECT 1 FROM dual WHERE 1=0;

  v1 number;
BEGIN
  OPEN c1;
  FETCH c1 INTO v1; -- this returns a record
  FETCH c1 INTO v1; -- this does not return a record
  IF c1%NOTFOUND THEN
    dbms_output.put_line('c1%NOTFOUND: TRUE');
  ELSIF c1%NOTFOUND IS NULL THEN
    dbms_output.put_line('c1%NOTFOUND: NULL');
  ELSE
    dbms_output.put_line('c1%NOTFOUND: FALSE');
  END IF;
  CLOSE c1;

  OPEN c2;
  FETCH c2 INTO v1; -- this does not return a record
  IF c2%NOTFOUND THEN
    dbms_output.put_line('c2%NOTFOUND: TRUE');
  ELSIF c2%NOTFOUND IS NULL THEN
    dbms_output.put_line('c2%NOTFOUND: NULL');
  ELSE
    dbms_output.put_line('c2%NOTFOUND: FALSE');
  END IF;
  CLOSE c2;
END;
/

The output of the script on Oracle APEX 4.1 is (I think APEX is running Oracle 11gR2, but you can easily run the script on any version):

c1%NOTFOUND: TRUE
c2%NOTFOUND: TRUE

Based on this test, %NOTFOUND will not be NULL after a fetch has been executed. This matches what the 10g and 11g documentation says in the initial description of the %NOTFOUND attribute. The note about the loop never exiting must be from an old version of the example. Since it's just a note, I'd says it's safe to trust the initial description and disregard the note.

Answer 3

I can find a situation where a fetch can fail:

declare
  i integer;
  cursor c is
    select 1 / 0 from dual;
begin
  open c;

  begin
    fetch c
      into i;
  exception
    when others then
      dbms_output.put_line('ex');
  end;

  if c%notfound is null then
    dbms_output.put_line('null');
  elsif c%notfound then
    dbms_output.put_line('true');
  else
    dbms_output.put_line('false');
  end if;
  close c;

end;

But this only makes your question stronger since it will evaluate to null, neither in 10g nor in 11g ...