# Re: Examples of SQL anomalies?

Date: Fri, 27 Jun 2008 14:29:20 -0700

Message-ID: <vqma641l1rqql3uhtllme0mqohbheqmruc@4ax.com>

-CELKO- <jcelko212_at_earthlink.net> wrote:

*>>> The question is, if these issues are due to the SQL specification or simply due to a problem in a specific SQL product. Or could it be, that the definition is not precise enough in some points, so that database vendors implemented it differently? <<*

*>*

*>Nope, it is the specs. All aggregate (set) functions begin by*

*>removing the NULLs from their parameter set, then if there is a*

*>DISTINCT option on the parameter, they remove redundant duplicates and*

*>finally do the operation (MIN, MAX, AVG, SUM, COUNT on what is left.*

*>Since an empty set has no elements upon which to apply an operation,*

*>SQL returns a NULL (okay, it should be an "undefined" if we were*

*>mathematically correct).*

No, it should be zero per mathematicians I have checked with.

*>In SQL as in Set Theory, equality (=) and grouping are not the same;*

*>the SUM() and the + are not the same. They are for different levels*

*>of abstraction. It makes senses after your first course with*

*>transfinite numbers -- the cardinality of Aleph Null is not the same*

*>as counting all the integers one by one, etc.*

Bafflegab. I have studied transfinite numbers; the area is irrelevant.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

I have preferences. You have biases. He/She has prejudices.Received on Fri Jun 27 2008 - 16:29:20 CDT