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From Ronald Rudy <ronchal...@gmail.com>
Subject Re: Perhaps a stupid question
Date Fri, 05 Feb 2010 14:39:34 GMT
Interesting, I'll take a look...

In the interest of portability (in case we ever swap out Derby for something else) I think
for now I'll use a separate column I build and use specifically for sorting.

On a somewhat related question as it pertains to indexes - if I have this prepared statement
(used frequently):

SELECT col0, col1 FROM mytable WHERE col0 = ? AND col1 = ? ORDER BY sortcol

Does it buy me anything to include the "sortcol" in the index along with "col0" and "col1"?
 If I should only index "col0" and "col1", does it buy me anything to add a second index with
just "sortcol" in it?


On Feb 5, 2010, at 9:25:00 AM, Rick Hillegas wrote:

> Hi Ron,
> 
> If what you need is a custom sort order for string data, you can plug in your own custom
collator. See Knut's blog for details on how to do this: http://blogs.sun.com/kah/entry/user_defined_collation_in_apache
> 
> You can also use generated columns to build user-defined ordering. See the following
writeup for advice on how to do this: http://java.sun.com/developer/technicalArticles/Database/javadb_10_5/index.html#Generated_Columns
> 
> If these solutions don't work for you, tell us more about what you need. We may be able
to suggest another solution or at least capture your requirements for a future enhancement.
> 
> Thanks,
> -Rick
> 
> 
> Ronald Rudy wrote:
>> Is there any way programmatically or otherwise to specify a java.util.Comparator
type object to sort a specific column?  I realize this flies in the face of any SQL standard
or convention, but it would be really helpful to me at the moment :).  And since Derby is
Java-based, I was wondering if there might be something "non-standard" I could do to support
it ....?
>> 
>> My alternative is to create an additional column in my database that will give me
the sorting I want (as it would be given by a custom Comparator class) using standard varchar
sorting, but this isn't preferable.
>> 
>> Thanks,
>>   -Ron
>>  
> 


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