Re: implementation of a many-to-many relationship

On 27 Feb 2002 at 14:06, Dalton Shane wrote:

> I need to implement a many-to-many relationship in PostgreSQL but don't
> know how to. I've trawled through the mailing lists but can't find
> anything, it's very easy to do in Access so it can't be that hard in
> PostgreSQL.
> 
> I created a linking table between two tables (voter, candidates) called
> c_voting, I then reference the two table's primary keys to create a
> composite primary key for c_voting.
> 
> However when I go to input data into c_voting I get a referential integrity
> error saying that the primary key of table voter doesn't match primary key
> of c_voting (which it shouldn't).

The actual error message would help us.

> I've tried everything I can think of for the last four days, but to no
> avail.
> 
> This is a central part of my thesis and I need to get it working as soon as
> possible.

Yeah, well, we all have deadlines.

> If anyone knows how to implement this I would be very very very grateful,
> I've read all the documentation I can find but it didn't help.
> 
> Many thanks in advance for any advice that you can offer.

I created your tables.  Then executed the following commands:

test=# insert into voter (v_number) values (1);
INSERT 1067044 1
test=# insert into candidates (c_number) values (123);
INSERT 1067045 1
test=# insert into c_voting values (1, 123);
INSERT 1067046 1

test=# select * from c_voting;v_number | c_number
----------+----------       1 |      123
(1 row)

I don't see the problem.

Perhaps you should supply your example which fails.  Mentioning the 
postgresql version might be helpful too.  These tests were run on  7.2.
-- 
Dan Langille
The FreeBSD Diary - http://freebsddiary.org/ - practical examples