problem z tabelą Opcje

[Bastion]

mam taka tabele :

Kod

a_id INT(8) UNSIGNED NOT NULL AUTO_INCREMENT,
a_name VARCHAR(128) NOT NULL DEFAULT '',
b_id INT(8) UNSIGNED NOT NULL
b_name VARCHAR(128) NOT NULL DEFAULT '',
PRIMARY KEY (a_id),
UNIQUE KEY a_name (a_name)

jak zaoperowac b_id i b_name aby b_id tez bylo primary, a b_name mialo atrybut unique w taki sposob aby dalo sie wprowadzic takie dane :

INSERT INTO tabela SET (a_id, a_name, b_id, b_name) VALUES (1, "aaa", 1, "aaa")
INSERT INTO tabela SET (a_id, a_name, b_id, b_name) VALUES (2, "bbb", 1, "aaa")

ale juz

INSERT INTO tabela SET (a_id, a_name, b_id, b_name) VALUES (2, "bbb", 2, "aaa")
nie ze wzgledu na uniqe b_name