[Hsqldb-developers] GROUP_CONCAT (was: SUM for Strings)

[Werner, W. <ma...@wo...>]

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Thanks Fred,

I implemented it that way. You were right, this was fairly straight forward.
Are you interested in the patches, should I post them somewhere?

Thanks for your help,
Wolfgang

fredt wrote:
> The correct thing to do is actually implement GROUP_CONCAT. Just check the 
> code base and find all the uses of Token.T_SUM and Expression.SUM. Then add 
> a new Token.T_GROUP_CONCAT and a new Expression.GROUP_CONCAT and some code 
> to handle this case to all the places where Token.T_SUM and Expression.SUM 
> are used. It's actually quite simple.
> 
> Fred
> 
> ----- Original Message ----- 
> From: "Werner, Wolfgang" <ma...@wo...>
> To: <hsq...@li...>
> Sent: 09 September 2005 01:35
> Subject: Re: [Hsqldb-developers] SUM for Strings
> 
> 
> Hi again,
> 
> I just noticed that my change breaks some of the unit tests. I'll have
> another look at it.
> 
> Sorry for bothering,
> Wolfgang
> 
> Werner, Wolfgang wrote:
> 
>>>Hi,
>>>
>>>I needed something similar to MySQLs GROUP_CONCAT and came up with the
>>>following hack:
>>>I simply added a concat operation for VARCHAR to the SUM function. This
>>>is my first contact with hsqldb, so if this patch is a bad idea please
>>>clarify.
>>>I guess it would be more consistent to add a completely new aggregate
>>>function, but does it do any harm this way?
>>>
>>>I didn't want to post it on the patch tracker since I'm new to the list
>>>and don't know if this is appropriate, so it is attached.
>>>
>>>Btw. hsqldb is really great work. Using it the first time today and
>>>already loving it. Thanks!
>>>
>>>Regards,
>>>Wolfgang
>>>
>>><diff args='-cb'>
>>>*** SetFunction.java Fri Jul  8 16:13:00 2005
>>>--- SetFunction.java.ww Fri Sep  9 02:22:26 2005
>>>***************
>>>*** 137,142 ****
>>>--- 137,150 ----
>>>                                  currentBigDecimal.add((BigDecimal) 
>>>item);
>>>                          }
>>>
>>>+                     case Types.VARCHAR:
>>>+                         if (currentValue == null) {
>>>+                             currentValue = (String) item;
>>>+                         } else {
>>>+                             currentValue =
>>>+ currentValue.toString().concat((String)item);
>>>+                         }
>>>+
>>>                          return;
>>>
>>>                      default :
>>>***************
>>>*** 266,271 ****
>>>--- 274,282 ----
>>>                      case Types.DECIMAL :
>>>                          return currentBigDecimal;
>>>
>>>+                     case Types.VARCHAR:
>>>+ return (String)currentValue;
>>>+
>>>                      default :
>>>                          throw Trace.error(Trace.SUM_OF_NON_NUMERIC);
>>>                  }
>>></diff>
> 
> 
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> 

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September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices
Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA
Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf
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