Bruce Momjian <maillist@candle.pha.pa.us> writes:
> That is an excellent point. GROUP BY has to use a column name, and they
> have to be unique, while WHERE does not require stuff to be in the
> target list, so there is a change of ambiguity. I am going to remove
> the item from the list.
Good point --- consider this:SELECT a, b AS a FROM tt GROUP BY a;
We do get it right: "ERROR: GROUP BY 'a' is ambiguous".
Whereas inSELECT a, b AS a FROM tt WHERE a = 1;
the WHERE clause is taken as referring to the "real" column a.
So, unless there's some violation of spec behavior here, there is a
reason for GROUP BY to behave differently from WHERE. I think I was
the one who complained that they were different --- I withdraw the
complaint.
BTW, which behavior should ORDER BY exhibit? I find thatSELECT a, b AS a FROM tt ORDER BY a;
is accepted and 'a' is taken to be the real column a. Considering that
ORDER BY is otherwise much like GROUP BY, I wonder whether it shouldn't
complain that 'a' is ambiguous...
regards, tom lane
