RE: How to do a Top-N analysis, while avoiding subqueries
- From: <tristan.van.essen@xxxxxxxxxxxxx>
- To: <msoyer@xxxxxxxxx>
- Date: Wed, 7 Jun 2006 12:09:23 +0200
Hi Muhammed
It's just a case study. Is it possible to do without the sub query?
Actually, the original question is not from me, but from a friend of mine. I
was just thinking about a good solution all morning long and couldn't figure
out a good answer to the question.
I find it quite reasonable to try a simple thing like a Top-N analysis without
the use of a (possibly costly) sub query.
But maybe I'm just spoiled by the proprietary MySQL feature of LIMIT BY...
Regards,
Tristan
------------------------------------------------------------------------------------
Tristan van Essen
Accenture Technology Solutions AG
Baslerstrasse 60
CH-8048 Zürich
Office: +41 44 405 3245
Mobile: +41 79 654 0592
Email: tristan.van.essen@xxxxxxxxxxxxx
________________________________
From: Muhammed Soyer [mailto:msoyer@xxxxxxxxx]
Sent: Mittwoch, 7. Juni 2006 12:02
To: van Essen, Tristan
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: How to do a Top-N analysis, while avoiding subqueries
Why dont you want to use sub queries ? Any solid reason or just for curiosity ..
2006/6/7, tristan.van.essen@xxxxxxxxxxxxx <tristan.van.essen@xxxxxxxxxxxxx>:
Hi folks, this is my first question in this mailing list.
How do you do a top-n analysis while avoiding subqueries, but still use group
functions on other columns?
I have following Query:
SELECT COUNT(city) quantity, city
FROM customer
GROUP BY city
ORDER BY quantity DESC;
This works fine so far with the exception that I only want the first record
returned, instead of all. I tried to solve the problem with the ROWNUM
function, but it won't work well. The problem here is that I must include
ROWNUM in the GROUP BY clause, else the query fails. But then the result isn't
right anymore. I wish there was any sort of LIMIT BY clause, like there is in
MySQL.
How can I solve this, while not using any subqueries?
Regards,
Tristan
------------------------------------------------------------------------------------
Tristan van Essen
Accenture Technology Solutions AG
Baslerstrasse 60
CH-8048 Zürich
Office: +41 44 405 3245
Mobile : +41 79 654 0592
Email: tristan.van.essen@xxxxxxxxxxxxx
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