Re: Distinct on a non-sort column

Cstdenis <lists@on-track.ca> writes:
> If I understand that you are proposing as

>     select * from
>                  (select distinct on (user_id) * from stories as s order
>     by user_id) as foo
>     order by date_submitted desc limit 10;

No, you always need to sort by *more* columns than are listed in
DISTINCT ON.  That's what determines which row is picked in each
DISTINCT group.  Read the SELECT reference page's example of how
to use DISTINCT ON.

            regards, tom lane