Re: Foreign key

On Fri, Mar 25, 2005 at 04:31:16PM +0100, ASAKALAL(at)bouyguestelecom(dot)fr wrote:
>
> When i add table with foreign key in my database, this error return : <
> number of referencing and referenced colums for foreign key disagree>.

Apparently the referencing key (the foreign key specification) has
a different number of columns than the referenced key (the primary
key or other unique key in the referenced table). Here's an example
that illustrates the problem:

CREATE TABLE foo (
pk1 integer NOT NULL,
pk2 integer NOT NULL,
PRIMARY KEY (pk1, pk2) -- 2-column primary key
);

CREATE TABLE bar (
fk integer NOT NULL REFERENCES foo -- 1-column foreign key
);

ERROR: number of referencing and referenced columns for foreign key disagree

In the above example we need a 2-column foreign key:

CREATE TABLE bar (
fk1 integer NOT NULL,
fk2 integer NOT NULL,
FOREIGN KEY (fk1, fk2) REFERENCES foo
);

Here's another example that references a 1-column unique key that
isn't a primary key:

CREATE TABLE foo (
pk1 integer NOT NULL,
pk2 integer NOT NULL,
x integer NOT NULL,
PRIMARY KEY (pk1, pk2),
UNIQUE (x)
);

CREATE TABLE bar (
fk integer NOT NULL REFERENCES foo (x)
);

If these examples don't help, then please post the table definitions
you're working with and explain what you'd like to do.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/