Just noticed you replied to me only. Send replies to the list. You can leave individuals cc'd. The convention here is also to inline your replies - top-posting is undesirable.
In any case, in order to write "select *" you have to group on both x and y at the same time. If you group on either column only, the query will fail. So the choice of x versus y is immaterial. Having grouped on x the text is explaining that the failure to also group on y is a problem.
I don't know that the existing wording is the most clear, but it is correct.
David J.
On Wed, Jul 24, 2024 at 8:02 AM Yaroslav Saburov <y.saburov@gmail.com> wrote:
>>because there is no single value for the column y that could be associated with each group.
