Referencing a view?

Hi,

Is there anyway that you can reference a column in a view for referential integrity? The problem is with the unique thing, obviously I can't create a unique index on a view. Here is what I have:

CREATE SEQUENCE "addresses_id_seq" start 1 increment 1 maxvalue 2147483647 minvalue 1 cache 1 ;

CREATE TABLE "org_addresses" (
"id" integer DEFAULT nextval('addresses_id_seq'::text) NOT NULL,
"orgid" integer references orgs on delete cascade,
"name" character varying(255),
"street1" character varying(255),
"street2" character varying(100),
"city" character varying(100),
"state" character(2),
"zip" character(10),
Constraint "org_addresses_pkey" Primary Key ("id")
);

CREATE TABLE "user_addresses" (
"id" integer DEFAULT nextval('addresses_id_seq'::text) NOT NULL,
"userid" integer references users on delete cascade,
"name" character varying(255),
"street1" character varying(255),
"street2" character varying(100),
"city" character varying(100),
"state" character(2),
"zip" character(10),
Constraint "user_addresses_pkey" Primary Key ("id")
);

CREATE VIEW "addresses" as SELECT user_addresses.id, user_addresses.userid, user_addresses.name, user_addresses.street1, user_addresses.street2, user_addresses.city, user_addresses.state, user_addresses.zip FROM user_addresses UNION SELECT org_addresses.id, NULL::unknown, org_addresses.name, org_addresses.street1, org_addresses.street2, org_addresses.city, org_addresses.state, org_addresses.zip FROM org_addresses;

So this gives me a view with every address, each with a unique id as I used the same sequence in both tables. Now what I want to do is something like this :

CREATE TABLE orders (
id serial primary key,
shipping_address int references addresses(id),
.
.
);

Which of course doesn't work because addresses as a view can't have a unique index. Any way around this?

- James