Re: big distinct clause vs. group by

Hi Robert,

Oh, I do care about these columns.
But by using an group by on the key columns, I cannot select the columns as
they are. Otherwise you get an error message.
So I have to use an aggregate functionlike min().

Best...
Uwe

On 19 April 2011 10:24, Robert Klemme <shortcutter(at)googlemail(dot)com> wrote:

> On Mon, Apr 18, 2011 at 7:13 PM, Uwe Bartels <uwe(dot)bartels(at)gmail(dot)com>
> wrote:
> > the aggregate function I was talking about is the function I need to use
> for
> > the non-group by columns like min() in my example.
> > There are of course several function to choose from, and I wanted to know
> > which causes as less as possible resources.
>
> If you do not care about the output of the non key columns, why do you
> include them in the query at all? That would certainly be the
> cheapest option.
>
> If you need _any_ column value you can use a constant.
>
> rklemme=> select * from t1;
> k | v
> ---+---
> 0 | 0
> 0 | 1
> 1 | 2
> 1 | 3
> 2 | 4
> 2 | 5
> 3 | 6
> 3 | 7
> 4 | 8
> 4 | 9
> (10 rows)
>
> rklemme=> select k, 99 as v from t1 group by k order by k;
> k | v
> ---+----
> 0 | 99
> 1 | 99
> 2 | 99
> 3 | 99
> 4 | 99
> (5 rows)
>
> rklemme=>
>
> Greetings from Paderborn
>
> robert
>
> --
> remember.guy do |as, often| as.you_can - without end
> http://blog.rubybestpractices.com/
>