Re: Rank

On Sun, 2 May 2004 02:22:37 +0800
"Muhyiddin A.M Hayat" <middink(at)indo(dot)net(dot)id> threw this fish to the penguins:

> I Have below table
>
> id | site_name | point
> ----+-----------+-------
> 1 | Site A | 40
> 2 | Site B | 90
> 3 | Site D | 22
> 4 | Site X | 98
>
> Would like to calc that Rank for each site, and look like
>
> id | site_name | point | rank
> ----+-----------+-------+------
> 1 | Site A | 40 | 3
> 2 | Site B | 90 | 2
> 3 | Site D | 22 | 4
> 4 | Site X | 98 | 1

Well, a simple minded solution would be:

select id,site_name,point,(select count(*)from mytable t2
where t2.point >= t1.point) as rank from mytable t1;

id | site_name | point | rank
----+-----------+-------+------
4 | Site X | 98 | 1
2 | Site B | 90 | 2
1 | Site A | 40 | 3
3 | Site D | 22 | 4
(4 rows)

If mytable is huge this may be prohibitively slow, but it's worth a try.
There's probably a self join that would be faster. Hmm... in fact:

select t1.id,t1.site_name,t1.point,count(t2.point) as rank from mytable t1,mytable t2
where t2.point >=t1.point group by t1.id,t1.site_name,t1.point;

id | site_name | point | rank
----+-----------+-------+------
3 | Site D | 22 | 4
2 | Site B | 90 | 2
4 | Site X | 98 | 1
1 | Site A | 40 | 3
(4 rows)

-- George Young
--
"Are the gods not just?" "Oh no, child.
What would become of us if they were?" (CSL)