Re: [SQL] Foreign key

[Michael Fuhr]

On Fri, Mar 25, 2005 at 04:31:16PM +0100, [EMAIL PROTECTED] 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/

---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?

               http://archives.postgresql.org