Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: mAsterdam <>
Date: Tue, 07 Jun 2005 00:11:11 +0200
Message-ID: <42a4c9fc$0$49036$>

Alexandr Savinov wrote:

> Paul schrieb:

>> Alexandr Savinov wrote:
>>> Assume that we have a set of 3 values S = {1, 3, 10}. We want to
>>> aggreage them and apply some function func: A = func(S). Do we have a
>>> problem? No. Now remove some item from the set so that we have S = {1,
>>> 3} and then apply again the aggregation function. Do we have a
>>> problem? No.
>>> Having null values is actually a way of removing data items from
>>> consideration. In this example we apply the aggregation function to the
>>> set {1, 3} which is equivalent to applying it to the set {1, 3, null}.
Most of the time, in database context NULL denotes, as you point out, the _absence_ of a value where you would expect one - still you are freely using "NULL value" as a special kind of value. ISTM this is inviting a lot of non-issues.

Did you consider viewing "NULL value" as a contradictio in terminis? Received on Tue Jun 07 2005 - 00:11:11 CEST

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