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From Rick Hillegas <rick.hille...@oracle.com>
Subject Re: help with sql query for Derby
Date Fri, 29 Apr 2011 12:54:33 GMT
Hi Luis,

Derby does not support a GROUP_CONCAT aggregate function. However, it 
would be trivial to write if we implemented DERBY-672, user-defined 
aggregates. By voting for that feature, you can boost its chances of 
being implemented in our next feature release.

Many performance-enhancing techniques can be found in the Derby Tuning 
Guide: 
http://db.apache.org/derby/docs/10.7/tuning/tuning-single.html#ctunoptimz39739 
If you describe your problem queries, the community may be able to help 
you speed them up.

Hope this helps,
-Rick


On 4/28/11 7:22 PM, Luis Ribeiro wrote:
> Dears,
>     My name is Luis Ribeiro, I`m brazilian and I study Computer 
> Science at Universidade Presbiteriana Mackenzie 
> (http://www.mackenzie.br/portal/principal.php). I and Henrique 
> Teixeira (cc) are on the last semester and we`re doing our final 
> project. To be honest, we`re finishing its. It`s about Comparison 
> between HD databases and In-Memory databases.
>     We`re trying to use Apache Derby to know how it works with the 
> simple systems that we developed.
>     We have two doubts and I would be greatfull if you could answer to us:
>     - Does exist some function or method that you use similar to 
> "GROUP_CONCAT" (from MySQL)? I want to know if I can do this on a 
> simple way with Apache Derby?
>
> Original table
> ID | NAME
> 1  | Luis
> 2  | Henrique
> 3  | Luis
>
> After do the query
> ID | NAME
> 1, 3 | Luis
> 2  | Henrique
>
>     - What we need to do to have a exceptional performance with In 
> Memory mode? I`d increased jvm heap, but it didn`t work.
>
>     I`m sorry if I was offensive with this e-mail.
>
>     Thank you very much.
>
> Best regards,
> Luis Ribeiro


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