oracle - 提取后％NOTFOUND可以返回null吗？

Question

This question提出了一个非常有趣的观点；在Oracle文档中，关于在获取后%NOTFOUND是否可能为null似乎存在矛盾。是吗？

引用11g documentation

Note: In Example 6-16, if FETCH never fetches a row, then c1%NOTFOUND is always NULL and the loop is never exited. To prevent infinite looping, use this EXIT statement instead: EXIT WHEN c1%NOTFOUND OR (c1%NOTFOUND IS NULL);

该文档似乎直接自相矛盾，因为它也表示以下内容，这意味着在获取 %NOTFOUND之后不能为空。

%NOTFOUND (the logical opposite of %FOUND) returns:
NULL after the explicit cursor is opened but before the first fetch
FALSE if the most recent fetch from the explicit cursor returned a row
TRUE otherwise

10g documentation也有类似的警告，这不一定是直接的矛盾，因为它警告为获取此行为可能无法成功执行获取操作。

Before the first fetch, %NOTFOUND evaluates to NULL. If FETCH never executes successfully, the EXIT WHEN condition is never TRUE and the loop is never exited. To be safe, you might want to use the following EXIT statement instead:

EXIT WHEN c1%NOTFOUND OR c1%NOTFOUND IS NULL;

在什么情况下，执行获取后，获取可能会失败，或者 %NOTFOUND返回null？

Answer 1

我发现一种提取可能失败的情况:

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;

但这只会使您的问题更强，因为无论在10g还是11g中，它都将评估为null……