[Monetdb-developers] semantics of aggregation operations

Niels Nes Niels.Nes at cwi.nl
Thu May 18 20:46:26 CEST 2006


On Thu, May 18, 2006 at 04:14:08PM +0200, Torsten Grust wrote:
> >[...]
> >A small detail of SQL spec that might be relevant:
> >If a column contains only NULL or no values at all the result of the
> >aggregate function is NULL.  COUNT is an exception, obviously.
> 
> Yes, I think it is relevant.  Because the semantics of SUM are as is,  
> a SQL query can tell an all-NULL column (yields NULL) from an empty  
> aggregation input set (yields 0).  I vote for the status quo.

The current sum (or any of the aggregates except count) has the problem
with NULLs. Allthough the SQL logics may not be perfect for everybody, just
adding yet another set of aggregates with other semantics isn't good
for maintainability. So I'd like you all to reconsider, ie clear reasons
why the current semantics are better and/or required.

Niels
> 
> Cheers,
>    --Teggy
> --
>   | Prof. Dr. Torsten Grust                         grust at in.tum.de |
>   |                                 http://www-db.in.tum.de/~grust/ |
>   |     Database Systems - Technische Universität München (Germany) |
> 
> 
> 
> 
> 
> 
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-- 

Niels Nes, Centre for Mathematics and Computer Science (CWI)
Kruislaan 413, 1098 SJ Amsterdam, The Netherlands
room C0.02,  phone ++31 20 592-4098, fax ++31 20 592-4312
url: http://www.cwi.nl/~niels   e-mail: Niels.Nes at cwi.nl




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