Re: Strange primary key constraint influence to grouping

>
>
> This is because PostgreSQL 9.1 added the feature of simple checking of
> functional dependencies for GROUP BY. The manual of 9.1 explains quite well
> when PostgreSQL considers there to be a functional dependency.
>
> "When GROUP BY is present, it is not valid for the SELECT list expressions
> to refer to ungrouped columns except within aggregate functions or if the
> ungrouped column is functionally dependent on the grouped columns, since
> there would otherwise be more than one possible value to return for an
> ungrouped column. A functional dependency exists if the grouped columns (or
> a subset thereof) are the primary key of the table containing the ungrouped
> column."
>
> I completely agree with documentation.

But my case shows that "not valid" expression which refers to column which
is ungrouped still works in 9.1.

G.