Hi,
I'm a final year computer science student working on a database project.
Basically I have two many-to-many relationships in my database but I don't know
how to implement this in PostgreSQL. Here's an example of what I'm talkinng
about.
I have a table voter and a table candidates. Because of the many-to-many
relationship between these two table, I created a linking table c_voting. I
reference both primary keys from voter and candidates to produce a composite
primary key for c_voting.
see tables below
However when I go to stick data in c_voting, I get a referential integrity
error, which says the primary key and foreign key don't match.
Basically the primary key in voter is an integer while the primary key in
c_voting is (integer, integer) ie. the two foreign keys.
The same happens for the candidate table.
The theory is sound, it's just the syntax that's killing me
How do I get over this problem?
I have to hand this thesis up in 2 weeks, so I'm getting desperate for any help
I can get.
Thanks in advance to those who may reply to this email
From
Shane.
CREATE TABLE voter (v_number integer NOT NULL PRIMARY KEY, v_name
varchar(20),v_surname varchar(20),v_birth date,v_address varchar(50),v_marital varchar(10),v_job
varchar(15)
);
CREATE TABLE candidates (c_number integer NOT NULL PRIMARY KEY, c_name
varchar(20),c_surname varchar(20),c_party varchar(20),c_constituency varchar(35)
);
CREATE TABLE c_voting (v_number integer NOT NULL CONSTRAINT cvote_ref_voter REFERENCES voter
ON UPDATE CASCADE ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED,
c_number integer NOT NULL CONSTRAINT cvote_ref_can REFERENCES candidates ON UPDATE
CASCADE ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED -- I tried these
combinationsbelow seperately but got nowhere--primary key(v_number, c_number)--foreign key (v_number) references voter
(v_number),--foreignkey (c_number) references candidates(c_number)
);
