Re: Order by YYYY MM DD in reverse chrono order trouble

Thank you and Denis (denis(at)coralindia(dot)com) - that was it. I needed
explicit DESC for each ORDER BY criterium.

Otis

--- Stijn Vanroye <s(dot)vanroye(at)farcourier(dot)com> wrote:
> > Hello,
> >
> > I am trying to select distinct dates and order them in the reverse
> > chronological order. Although the column type is TIMESTAMP, in
> this
> > case I want only YYYY, MM, and DD back.
> >
> > I am using the following query, but it's not returning dates back
> in
> > the reverse chronological order:
> >
> > SELECT DISTINCT
> > date_part('year', uu.add_date), date_part('month', uu.add_date),
>
> > date_part('day', uu.add_date)
> >
> > FROM uus INNER JOIN ui ON uus.user_id=ui.id INNER JOIN uu ON
> > ui.id=uu.user_id
> > WHERE uus.x_id=1
> >
> > ORDER BY
> > date_part('year', uu.add_date), date_part('month', uu.add_date),
> > date_part('day', uu.add_date) DESC;
> >
> >
> > This is what the above query returns:
> >
> > date_part | date_part | date_part
> > -----------+-----------+-----------
> > 2004 | 2 | 6
> > 2004 | 4 | 20
> > (2 rows)
> >
> >
> > I am trying to get back something like this:
> > 2004 4 20
> > 2004 4 19
> > 2004 2 6
> > ...
> >
> > My query is obviously wrong, but I can't see the mistake. I was
> > wondering if anyone else can see it. Just changing DESC to ASC,
> did
> > not work.
> >
> > Thank you!
> > Otis
> What you could try to do in your order by clause is the following:
> ORDER BY
> date_part('year', uu.add_date) DESC,
> date_part('month', uu.add_date) DESC,
> date_part('day', uu.add_date) DESC;
> That way you are sure each of the fields is sorted DESC. if you don't
> specify a direction in your order by clause postgres will take ASC as
> the default. I think that he does "ASC,ASC,DESC" instead. I'm not
> sure if he applies the DESC to all specified fields in the order by
> if you declare it only once.
>
>
> Regards,
>
> Stijn Vanroye
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if
> your
> joining column's datatypes do not match