By commenting the GROUP BY the query no longer parses, so doesn't run.
Of course!!! D'oh.
I suppose, what you could do, is pass your entire GROUP BY statement, then end that statement, start a new one and then add the line comment. That is asking quite a lot at that stage (nor am I saying that someone else would not work that out and do it).
Thom~
Excuse my typos and sometimes awful grammar. My fingers work faster than my brain does.
Larnu.uk