create table countries (
id serial unique,
country_name text not null,
country_prefix text,
country_shortname text not null
);

create table users (
id serial unique,
username text not null,
password text not null,
hostip text
);

create table dids (
country_id integer references countries (id),
user_id integer references users (id),
assigned char constraint assigned in ('Y','N','P'),
did text not null
);