Does Codd's view of a relational database differ from that of Date&Darwin? [M.Gittens] - comp.databases.theory

Message from discussion Does Codd's view of a relational database differ from that of Date&Darwin? [M.Gittens]

Jarl Hermansson

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More options Jun 8 2005, 8:51 pm

Newsgroups: comp.databases.theory

From: Jarl Hermansson <j...@mimer.com>

Date: Wed, 8 Jun 2005 10:51:14 +0000 (UTC)

Local: Wed, Jun 8 2005 8:51 pm

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

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Paul <p...@test.com> wrote in
news:42a6c7bd$0$32618$ed2619ec@ptn-nntp-reader02.plus.net:

> I'd rather the SUM of a column containing a NULL return NULL. If I
> want to override the behaviour, I can always do a SUM(COALESCE(col)).
> But if the default is to treat NULLs as zero, I can't manually
> override it to the behaviour I want.

> At least MSSQL warns you that it's eliminated a NULL from an
> aggregate, although that's not much use if you're not running the
> query interactively.

Paul,

That's not really a MS SQL Server feature, its according to the ISO/ANSI
SQL standard.

SQL-99:
----
6.16 <set function specification>

General Rules
1) Case:
a) If COUNT(*) is specified, then the result is the cardinality of T.

b) Otherwise, let TX be the single-column table that is the result of
applying the <value expression> to each row of T and eliminating null
values. If one or more null values are eliminated, then a completion
condition is raised: warning — null value eliminated in set function.
----
(SQLSTATE is set to 01003)

Regards,
Jarl

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