CASE vs DECODE - CASE with SUM and All in Page Item is non aggregable

Question

Hi,
I'm using Discoverer 9.0.4.
After switching calculations from DECODE to CASE
I found out that case gives a non aggregable result when using a Page Item and selecting <All>.
The calculations
(SUM x) / (SUM y)
or
(x SUM) / (y SUM)
where x and y are variables, work fine with page item <All>.
But for example:
CASE WHEN 1=2 THEN 1 ELSE (SUM x) / (SUM y) END
gives non-aggregable.
The same code works with DECODE:
DECODE(1,2,1,(SUM x) / (SUM y))
and is aggregable.
Does anyone know a reason or a way to make it work with CASE?
Thanks,
Joao Noronha
P.S.: I wanted <= comparisons and CASE is the best in simplicity,
but now I know I can do it with DECODE, still looking ok using LEAST instead of ABS of the difference.

Answer 1

Hi there
I think therefore you have answered your own question and determined that using CASE in aggregations is not a good idea. I only threw out the two CASE options as ideas not as solutions, just in case (pardon the pun) one of these worked in your situation.
Your comment I must say that if it worked it would give a wrong result (the sum of the divisions is not the same as the division of the sums) may give the wrong answer in your case but may be correct in others. It just depends how the items in the folder have been set up. I agree though that SUM(x) / SUM(y) will more often than not give the right answer.
This discussion about DECODE vs CASE has been going on ever since Oracle introduced CASE as a means of placating a younger breed of user who needed an IF..THEN...ELSE construct and could not get their minds around the intricacies of DECODE. The DECODE is a much more reliable function than CASE because it has been around for a long time allowing Oracle plenty of opportunity to iron the bugs out of it. If I get a chance I will always use a DECODE whenever aggregations are required. However, when no aggregations are in use then I'll use CASE, simply because it's easier for users to work with.
Unfortunately, users need to work with aggregations and so I don't see any alternative to Plus users having to learn DECODE. Whenever I teach Plus I always teach the users both CASE and DECODE but point out that DECODE has fewer issues that CASE. Oh, and talking of issues, try getting the THEN and ELSE components to return a different datatype. CASE has a fit and will not compile.
Best wishes and glad you got your issue solved - you did right?
Regards
Michael