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* Quartile (etc) ranking in a SQL statement?
@ 2002-11-07 18:16 Jeff Boes <jboes@nexcerpt.com>
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Boes @ 2002-11-07 18:16 UTC (permalink / raw)
To: pgsql-sql
Here's a puzzler:
Given a query that returns rows ranked by some criteria, how can I write
another query around it that will give me the (say) first quartile (top
25%)? Another way of putting it is: if I have rows that look like this:
aaa | 1251
aba | 1197
cax | 1042
... | ...
axq | 23
(142 rows)
How can I write a query that will return these as
1 | aaa | 1251
2 | aba | 1197
3 | cax | 1042
... | ... | ...
142 | axq | 23
--
Jeff Boes vox 616.226.9550 ext 24
Database Engineer fax 616.349.9076
Nexcerpt, Inc. http://www.nexcerpt.com
...Nexcerpt... Extend your Expertise
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Quartile (etc) ranking in a SQL statement?
@ 2002-11-07 20:50 Jean-Luc Lachance <jllachan@nsd.ca>
parent: Jeff Boes <jboes@nexcerpt.com>
0 siblings, 0 replies; 2+ messages in thread
From: Jean-Luc Lachance @ 2002-11-07 20:50 UTC (permalink / raw)
To: Jeff Boes <jboes@nexcerpt.com>; +Cc: pgsql-sql
In a PLPGPSQL script, once you know count(*) try
execute ''select * from table limit '' || int4( theCount / 4);
If you want numbering, create a sequence and add nextval() to the query.
JLL
Jeff Boes wrote:
>
> Here's a puzzler:
>
> Given a query that returns rows ranked by some criteria, how can I write
> another query around it that will give me the (say) first quartile (top
> 25%)? Another way of putting it is: if I have rows that look like this:
>
> aaa | 1251
> aba | 1197
> cax | 1042
> ... | ...
> axq | 23
> (142 rows)
>
> How can I write a query that will return these as
>
> 1 | aaa | 1251
> 2 | aba | 1197
> 3 | cax | 1042
> ... | ... | ...
> 142 | axq | 23
>
> --
> Jeff Boes vox 616.226.9550 ext 24
> Database Engineer fax 616.349.9076
> Nexcerpt, Inc. http://www.nexcerpt.com
> ...Nexcerpt... Extend your Expertise
>
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2002-11-07 18:16 Quartile (etc) ranking in a SQL statement? Jeff Boes <jboes@nexcerpt.com>
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