Hi,

don't know how to call this... It's not circular references, rather
references where you have multiple paths between two tables, like
this:

A->C
A->B
B->D
C->D

or

A->B
B->C
A->C

etc.

1. How do you call this?
2. Is it bad design by default?
3. Is it bad design if your database is full of this kind of reference
paths?

Also, if you have a link to a document that talks about this and other
database design patterns, I'd love to hear.

On 2010-04-22 13:20, Willem Fischer wrote:
Adjancy list is one commonly used term

No, not necessarly. It all depends on the requirements. Given the tuples
(A,B), (B,C) the tuple (A,C) may or may not be redundant. Say for
example that we are representing the relation PARENT. A is a parent of B
and B is a parent of C does not imply that A is a parent of C. In those
(hopefully rare :-) cases where A is a parent of both B and C, this has
to be recorded as a separate tuple, i.e. (A,C).

Not sure if it is what you are looking for, but you can check out:

http://citeseerx.ist.psu.edu/viewdoc...i=10.1.1.48.53

Troels Arvin has a nice list of articles etc. regarding hierarchical data:

http://troels.arvin.dk/db/rdbms/links/


/Lennart

Willem Fischer wrote:
IMS ... ;-)

May be you can find the answers to your other questions here:
http://tinyurl.com/36zwdf9

--
Jeroen

On Apr 22, 1:49*pm, Lennart Jonsson <erik.lennart.jons... (AT) gmail (DOT) com>
wrote:
What I actually meant was references between several tables, not a
recursive reference on one table.

Any "Best Practice" about that?