Hi,
I'm not sure why there is a reason for such behaviour.
For this table:
create table bg(id serial primary key, t text);
This works:
select count(id) from bg;
This works:
select count(distinct id) from bg;
And this doesn't:
select count(distinct id) from bg order by id;
ERROR: column "bg.id" must appear in the GROUP BY clause or be used in an
aggregate function
LINE 1: select count(distinct id) from bg order by id;
thanks,
Szymon