Comments on: T-SQL Tuesday – HAVING Puzzle answer

By: Alvin

Alvin — Wed, 20 Oct 2010 23:39:55 +0000

It seems that Oracle handles this differently.

Here is the result from Oracle Database 10g Enterprise Edition Release 10.2.0.4.0

SELECT ‘No rows’
FROM DUAL
WHERE 1=2
HAVING 1=1
;
no rows selected

By: Rob Farley

Rob Farley — Thu, 21 Jan 2010 05:47:24 +0000

Thanks Alvin.

If you have the time (and if you notice this comment), could you try:

SELECT dummy
FOM DUAL
HAVING 1=1;

In SQL, this would give an error, because it would force grouping to occur and then not know which value to use (despite there being only one). I suspect that Oracle might be seeing the 1=1 and ignore the line.

Again, thanks so much for your comment!

Rob

By: Rob Farley

Rob Farley — Thu, 14 Jan 2010 23:04:06 +0000

This got discussed at http://forum.lessthandot.com/viewtopic.php?f=17&t=9479 – and my quick answer for those people is: “Using HAVING (or a GROUP BY, DISTINCT or any aggregate function) means that any rows returned refer to groups not records. In this case, there is one group, containing no records.”