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On Wed, 21 Jul 1999, Darko Cvagic wrote:
> What does it means that GADFLY is Relational ?

Because Gadfly is almost Yet Another SQL Engine (not that I am against
Gadfly or SQL).

> How can I make relations between tables in database?

SELECT t1.bor, t1.belt, t2.der
FROM table1 t1, table2 t2
WHERE t1.plux = t2.flax

Oleg.
----
Oleg Broytmann Netskate/Inter.Net.Ru phd@emerald.netskate.ru
Programmers don't die, they just GOSUB without RETURN.

Oleg Broytmann wrote:

> On Wed, 21 Jul 1999, Darko Cvagic wrote:
> > What does it means that GADFLY is Relational ?
>
> Because Gadfly is almost Yet Another SQL Engine (not that I am against
> Gadfly or SQL).
>
> > How can I make relations between tables in database?
>
> SELECT t1.bor, t1.belt, t2.der
> FROM table1 t1, table2 t2
> WHERE t1.plux = t2.flax
>

SQL is a query langage, OSQL is an extension to OODBMS (Object oriented).

The "relationnal" model is an old model of data [1] but it as a theorical
background
with set theory, and it is widely spread in the industry.
Say you have a set of tables, each table can be viewed as
the subset of the cartesian product of to sets.

For more info, I think you can read some good books about
DBMS history, such as [2].

[1] The Entity-Relationship model - toward a unified view of data
P.P.-S. Chen, MIT, Readings in Database systems, M.Stonebraker,
Morgan Kaufmann, 1988
[note: paper is from ACM 1976]

[2] Principle of database systems - J. D. Ullman, Computer
science press1982

Marcvs [.alias Hum, I'm quite pleased about this pedantic and obscure answer. ]

In article <3795C21F.A0F13648@onera.fr>,
poinot@onera.fr wrote:

> SQL is a query langage, OSQL is an extension to OODBMS (Object
oriented).
>
> The "relationnal" model is an old model of data [1] but it as a
theorical
> background
> with set theory, and it is widely spread in the industry.

Yes and the primary difference between an RDBMS and an OODBMS is
that if something doesn't work in an RDBMS it's a bug, whereas
if something doesn't work in an OODBMS it's a feature, in fact
an indispensible and highly useful feature of great importance ;).

[note smiley]

-- Aaron Watters http://www.chordate.com

====

http://starship.skyport.net/crew/aaron_watters/bplustree/term.cgi?
2393368


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Marc POINOT wrote:
>
> Oleg Broytmann wrote:
>
> > On Wed, 21 Jul 1999, Darko Cvagic wrote:
> > > What does it means that GADFLY is Relational ?
> >
> > Because Gadfly is almost Yet Another SQL Engine (not that I am against
> > Gadfly or SQL).
> >
> > > How can I make relations between tables in database?
> >
> > SELECT t1.bor, t1.belt, t2.der
> > FROM table1 t1, table2 t2
> > WHERE t1.plux = t2.flax
> >
>
> SQL is a query langage, OSQL is an extension to OODBMS (Object oriented).
>
> The "relationnal" model is an old model of data [1] but it as a theorical
> background
> with set theory, and it is widely spread in the industry.
> Say you have a set of tables, each table can be viewed as
> the subset of the cartesian product of to sets.
>
> For more info, I think you can read some good books about
> DBMS history, such as [2].
>
> [1] The Entity-Relationship model - toward a unified view of data
> P.P.-S. Chen, MIT, Readings in Database systems, M.Stonebraker,
> Morgan Kaufmann, 1988
> [note: paper is from ACM 1976]
>
> [2] Principle of database systems - J. D. Ullman, Computer
> science press1982
>
> Marcvs [.alias Hum, I'm quite pleased about this pedantic and obscure answer. ]

Thanks, I think that I'm exchange terms like RELATION and LINK
So, Gadfly IS RELATIONAL, but I can't make something like:
CREATE LINK order_customer
FOREIGN KEY order(cno)
REFERENCES customer
ON DELETE RESTRICT

I can't do it in gadfly, am I wright?
What is name for construction like this?
I was thought that it is RELATIONAL , I was wrong!

Darko Cvagic writes:

> Thanks, I think that I'm exchange terms like RELATION and LINK
> So, Gadfly IS RELATIONAL, but I can't make something like:
> CREATE LINK order_customer
> FOREIGN KEY order(cno)
> REFERENCES customer
> ON DELETE RESTRICT
>
> I can't do it in gadfly, am I wright?
> What is name for construction like this?
> I was thought that it is RELATIONAL , I was wrong!

CREATE LINK is not in the ANSI standard at all. In the standard,
you'd do this in the CREATE TABLE statment.

The 86 level of the standard doesn't even have FOREIGN KEY or
REFERENCES.

The term "relational" can mean all kinds of things. I've seen it used
(by big-wigs in the field) to discard DBs that were based on
inverted-list technology as "non-relational" despite their having
full ANSI SQL capabilities.

- Gordon

On Wed, 21 Jul 1999 17:42:55 +0200, Darko Cvagic
<darko.cvagic@arcus.tel.hr> declaimed the following in comp.lang.python:

>
>
> Thanks, I think that I'm exchange terms like RELATION and LINK
> So, Gadfly IS RELATIONAL, but I can't make something like:
> CREATE LINK order_customer
> FOREIGN KEY order(cno)
> REFERENCES customer
> ON DELETE RESTRICT
>
> I can't do it in gadfly, am I wright?
> What is name for construction like this?
> I was thought that it is RELATIONAL , I was wrong!

That sounds like a definition of referential integrity
constraints... I've not looked at gadfly -- perhaps it doesn't actually
maintain such internally, but only via SQL select statements, which
would require one to code the integrity tests themselves...


It is confusing in a way -- based upon some readings of my old
DB textbooks, "relation" in "relational" doesn't really apply to
linkages between tables. The "relation" is that the key value /in/ the
table uniquely identifies the "related" data values, and that each
"record" (tuple in the texts) of a table is identical in format to every
other in that table.

Relational algebra and calculus are methods of selecting data
from multiple tables to produce a result -- but again, these do not
enforce referential integrity. In truth, "relational" is a view of the
data, which may be stored in any format -- even in hierarchical or
network format.

I think I begin to ramble...

--
> ============================================================== <
> wlfraed@ix.netcom.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> ============================================================== <
> Bestiaria Home Page: http://www.beastie.dm.net/ <
> Home Page: http://www.dm.net/~wulfraed/ <

From: wlfraed@ix.netcom.com (Dennis Lee Bieber)
Subject: Re: gadfly RDBMS ???
Organization: > Bestiaria Support Staff < > Dueling Modems Online Service <

On Wed, 21 Jul 1999 17:42:55 +0200, Darko Cvagic
<darko.cvagic@arcus.tel.hr> declaimed the following in comp.lang.python:

>
>
> Thanks, I think that I'm exchange terms like RELATION and LINK
> So, Gadfly IS RELATIONAL, but I can't make something like:
> CREATE LINK order_customer
> FOREIGN KEY order(cno)
> REFERENCES customer
> ON DELETE RESTRICT
>
> I can't do it in gadfly, am I wright?
> What is name for construction like this?
> I was thought that it is RELATIONAL , I was wrong!

That sounds like a definition of referential integrity
constraints... I've not looked at gadfly -- perhaps it doesn't actually
maintain such internally, but only via SQL select statements, which
would require one to code the integrity tests themselves...


It is confusing in a way -- based upon some readings of my old
DB textbooks, "relation" in "relational" doesn't really apply to
linkages between tables. The "relation" is that the key value /in/ the
table uniquely identifies the "related" data values, and that each
"record" (tuple in the texts) of a table is identical in format to every
other in that table.

Relational algebra and calculus are methods of selecting data
from multiple tables to produce a result -- but again, these do not
enforce referential integrity. In truth, "relational" is a view of the
data, which may be stored in any format -- even in hierarchical or
network format.

I think I begin to ramble...

--
> ============================================================== <
> wlfraed@ix.netcom.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> ============================================================== <
> Bestiaria Home Page: http://www.beastie.dm.net/ <
> Home Page: http://www.dm.net/~wulfraed/ <
--
|Fidonet: UUCP 2:500/3.1
|Internet: UUCP@p1.f3.n500.z2.hccfido.hcc.nl
|
| Standard disclaimer: The views of this user are strictly his own.

Darko Cvagic wrote:
>
> Thanks, I think that I'm exchange terms like RELATION and LINK
> So, Gadfly IS RELATIONAL, but I can't make something like:
> CREATE LINK order_customer
> FOREIGN KEY order(cno)
> REFERENCES customer
> ON DELETE RESTRICT
>
> I can't do it in gadfly, am I wright?
> What is name for construction like this?
> I was thought that it is RELATIONAL , I was wrong!

I think you're confused about the meaning of the term
"relational" in this context. In relational database
terminology, "table" and "relation" are synonymous.

"Relation" is a mathematical term for a set of tuples.
The tables in a relational database can be thought of
as mathematical relations. Each row (tuple) of the
table "relates together" the data items that it
contains, hence the name. Relations have some nice
mathematical properties which make them good for
building a database out of, and there is a large
body of theory on the subject.

Just to be confusing, a relation in a relational
database isn't necessarily the same thing as a
relationship in an entity-relationship model.
A relation (table) could be used to represent either
entities or relationships in an ER model.

Furthermore, although there are relationships
(in the non-technical sense) between different
tables, as far as the relational model is concerned,
they are implicit. You don't have to explicitly
declare "links" between tables. Some relational
database systems allow you to do so if you want,
for efficiency reasons, but they don't require
you to. If they did, they wouldn't qualify as
relational.

The same goes for indexes, key declarations,
integrity constraints, etc. etc. They're optional
extras to the basic relational model which
Gadfly doesn't provide -- but that doesn't mean
Gadfly isn't relational!

Hope that helps,
Greg

In article <37969382.C25210F4@compaq.com>,
Greg Ewing <greg.ewing@compaq.com> wrote:
> The same goes for indexes, key declarations,
> integrity constraints, etc. etc. They're optional
> extras to the basic relational model which
> Gadfly doesn't provide -- but that doesn't mean
> Gadfly isn't relational!

Ahem. Gadfly *does* provide indices. And a unique index
functions the same as a key constraint.

More complex integrity constraints are not provided,
but would be nice.

-- Aaron Watters

===

Doing business with some people is like
petting a skunk.
It's a learning experience
you don't care to repeat.


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