Re: Examples of SQL anomalies?

From: Gene Wirchenko <>
Date: Fri, 27 Jun 2008 14:29:20 -0700
Message-ID: <>

-CELKO- <> 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.


Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.
Received on Fri Jun 27 2008 - 23:29:20 CEST

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