alienalert=> \d account_role
                           Table "public.account_role"
   Column   |  Type   |                         Modifiers
------------+---------+-----------------------------------------------------------
 id         | integer | not null default nextval('account_role_id_seq'::regclass)
 account_id | integer | not null
 role_id    | integer | not null
 pool_id    | integer |
Indexes:
    "pk_account_role" PRIMARY KEY, btree (id)
    "unique_account_role_pool" UNIQUE, btree (account_id, role_id, (COALESCE(pool_id, (-1))))
Foreign-key constraints:
    "fk_account" FOREIGN KEY (account_id) REFERENCES account(id)
    "fk_pool" FOREIGN KEY (pool_id) REFERENCES pool(id)
    "fk_role" FOREIGN KEY (role_id) REFERENCES role(id)