Store a graph in a relational DB

Question

Greeting Gurus
How you would recommend to store a graph (vertices and links ) into a relational database ??
Or the way relational database organize data might not be the optimal to store a graph ??
And hence its operation such as sales man problem ??
Thanks so much

Answer 1

Hi,
vxwo0owxv wrote:
Thanks for the input. This is a way to get this done
I am curious about if it is possible to define a function when creating a unqiue index such that
if mod(a,b) = 1 then a & b are the same
e.g mod(5,4) = mod(7,3) = 1 so if I have (5,4) in my table I do not want (7,3)
so basically if it is possible to define a function and if the function in the data element return some pre-defined value then they would be considered the same.
maybe it is not the design intention of a relational database as such ??
This is a separate problem, so it would be better if you started a separate thread for it.  (You might be planning to constrain a graph table this way, but it's a separate problem, even if it's the same table.)
Yes, you can have function-based indexes, and they can be unique.
It's unclear what you're saying.
If MOD (a, b) = 1, then a and b are definitely NOT the same.  Only if MOD (a, b) = 0 can  a and b be the same, and even then, they are not necessarily the same.  That is, if a = b, then MOD (a, b) must be 0, but if MOD (a, b) = 0, it may be the case that a != b.  MOD (4, 4) = 0, but MOD (12, 4) = 0 also.
If you have a table and an index like this:
CREATE TABLE table_x
(   a    NUMBER (6, 0)
,   b    NUMBER (6, 0)
CREATE UNIQUE INDEX  x_a_mod_b ON table_x (MOD (a, b));
then you can INSERT either of these rows, but not both of them.
INSERT INTO  table_x (a, b) VALUES (5, 4);
INSERT INTO  table_x (a, b) VALUES (7, 3);
If row (5,4) is already in the table, and you try to INSERT (7, 3), then you'll get an error like this:
INSERT INTO  table_x (a, b) VALUES (7, 3)
ERROR at line 1:
ORA-00001: unique constraint (FUBAR.X_A_MOD_B) violated