Re: WWW/Internet 2009: 2nd CFP until 21 September x
Date: Sat, 15 Aug 2009 11:13:18 -0300
paul c wrote:
> Walter Mitty wrote: > ... >
>> The way I think of it is that every table with nulls in it is a
>> materialized outer join. If you can decompose the table into multiple
>> tables each of which has no nulls, what you discover is that a null in
>> the combined table corresponds to an absent row in one of the
>> decomposed tables.
>> Let me shift gears back into practical mode for a minute. In any
>> database I've ever worked with, the majority of columns are not a
>> primary key, or a foreign key or a part of a primary or foreign key,
>> or ever appear in a where of having clause.
But they often appear in aggregates, which makes my earlier example particularly grave:
SUM(A)+SUM(B) doesn't always equal SUM(A)+SUM(B) let alone SUM(A+B)
>> But I guess comments like this one are out of place in a theory
No, they are stupid and uninformed no matter what newsgroup you post them in.
> From what I've seen, SQL discards much of the available theory on the > grounds that early implementors couldn't see how to respect all aspects. > The small theory is replaced with blow-by-blow commentary for all the > special cases. It's pretty clear that many of those people weren't able > to distinguish the new theory from their previous experience, eg., Jim > Gray couched most of his writing about db in terms of operating systems. > They were all bright people, no doubt earnest too, but today we have > more experience.Received on Sat Aug 15 2009 - 09:13:18 CDT