Multiple keys?

In order to get the foreign key I want working, I had to have two unique
references on the parent table, though the second covers two columns that are
contained within the first. Is this wise? Is there a better way?

create table "package_info" (
"info_id" integer not null unique default
nextval('package_info_info_id_seq') primary key,
"package_id" integer not null references "packages" ("package_id"),
"package_version" varchar(16) not null default '0.0.1',
"info_type" varchar(32) not null default 'extra_data',
"info_value" text not null default 'Default',
unique ("package_id", "package_version", "info_type"),
unique ("package_id", "package_version")
);

create table "box_packages" (
"install_id" integer not null unique default
nextval('box_packages_install_id_seq') primary key,
"box_id" integer not null references "boxes" ("box_id"),
"package_id" integer not null,
"package_version" varchar(16) not null,
"install_date" timestamp with time zone not null,
"uninstall_data" timestamp with time zone,
foreign key ("package_id", "package_version") references
"package_info" ("package_id", "package_version"),
unique ("box_id", "package_id", "package_version", "install_date")
);

Danke,

--
Casey Allen Shobe / Network Security Analyst & PHP Developer
SecureWorks, Inc. / 404.327.6339 x169 / Fax: 404.728.0144
cshobe(at)secureworks(dot)net / http://www.secureworks.net
Content is my own and does not necessarily represent my company.