count distinct and group by

[Szymon Guz <mabewlun@xxxxxxxxx>]

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