Re: big distinct clause vs. group by

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/