It's not a problem as long as you know what you're doing. However, many programmers do not understand that "correct result" they're getting from such query is by chance not by design and it can become incorrect when data changes in the future.

>Not in any case. For example if you have a 1 to n and sum all n's and display fields from the 1's then the PK is the only thing you really need. The rest will be from the 1 record anyway. So it's a lot of superfluous work to check each non aggregate for changes. I found it to much work to redesign all the views etc and stuck with the old behavior.