I have a database design questions. How can we specify one of two
columns in a table should be not null? In other words, if one column is
null then another column should not be null. Here is an example. Let's
say we have document and we need to specify permissions to the

We use these terms a lot: conceptual, logical, physical.
I believe I have a good intuitive understanding of these
terms and how they are used. However, an intuitive
understanding and a formal definition are not the same

The wikipedia article on Codd's Twelve Rules (looks like a Baker's Dozen
 to me, maybe one is allowed to ignore any single one of them!) says:
Rule 5: The comprehensive data sublanguage rule:
 The system must support at least one relational language that

At the risk of being labeled a crank...
I'm looking for someone to tell me whether my idea for improving the
ANSI Join syntax has any merit.  One thing about the current syntax
that often strikes me is I usually join tables on identically named

There's a lot of terminological discussion floating around right now,
and some of it is really bad.
Most basically, a relation is a subset of a product of sets.
In the c.d.t. context, we mean a little more than that, because

http://news.yahoo.com/s/pcworld/20060621/tc_pcworld/126195
It looks like MySpace gathered a lot of data of some value. (What kind
business doesn't -- duh!) Therefore, price it properly and sell it. A
user want to query some data -- then provide an an interface to query

Tony,
If you think you somehow help others by continuing a discussion with a
retard, we have news for you.
It is severely detrimental to the c.d.t newsgroup quality and hurting

I was mad and I called him names. My problem is that I try to hold the
relational model in my head, and it's get hard once you beyond the simple
stuff. So Bob, sorry.
Rich

multidimensional..."
BB replies: The SQL table is multidimensional--or more correctly has a
number of dimensions equal to its degree--no matter the medium in which

Cimode,
You do not really give a damn about your judeo christian
heritage I respect it though ... I bet if we were face to
face you would have checked the thread about RAM memory

Can you give me some samples of RDMBS? Like FoxPro, Access
Thanks in advance ;)
BB

I'm helping a friend to build a system to handle advertisments from
local dealers in different regions/cities. In this system, an
advertisment belongs to a region and is connected to one or more
categories (in this context called searchwords).

what's difference between sql-dbms and rdbms ?
would you show me the theory model about the two dbms or any famous books
about it ?
thanks!

I am working on an application which need a data model that reflects
the schema structure. My tables are ("*" indicates primary key column):
tableinfo(*table_name)
columninfo(*table_name, *col_name)

This one is too easy...I will propose it for debunkning quote of the
week...
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