Re: When is a record NULL?

On Jul 24, 2009, at 2:59 PM, David E. Wheeler wrote:

> FETCH have INTO rec_have;
> FETCH want INTO rec_want;
> WHILE NOT rec_have IS NULL OR NOT rec_want IS NULL LOOP
> IF rec_have IS DISTINCT FROM rec_want THEN
> RETURN false;
> END IF;
> rownum = rownum + 1;
> FETCH have INTO rec_have;
> FETCH want INTO rec_want;
> END LOOP;
> RETURN true;

Bah. It fails to do what I want when I pass cursors that return:

VALUES (NULL, NULL), (NULL, NULL)
VALUES (NULL, NULL)

So when it gets to that second row in the first cursor, it doesn't
know it's a row with NULLs as opposed to an empty row. So this bit:

WHILE NOT rec_have IS NULL OR NOT rec_want IS NULL LOOP

Obviously isn't detecting the difference. I tried

WHILE (NOT rec_have IS NULL AND rec_have IS DISTINCT FROM NULL)
OR (NOT rec_want IS NULL AND rec_want IS DISTINCT FROM NULL)

and

WHILE (NOT rec_have IS NULL AND NOT rec_have IS NOT DISTINCT FROM
NULL)
OR (NOT rec_want IS NULL AND NOT rec_want IS NOT DISTINCT FROM
NULL)

But they didn't work, either.

There's got to be a way to do this; better, there ought to be an easy
way to tell the difference. :-(

Thanks,

David