多对一（产品只能有一家商店）
create table store( id int unsigned not null auto_increment, store_name varchar(30) not null, primary key(id));Query OK, 0 rows affected (0.02 sec)create table product( id int unsigned not null auto_increment, store_id int unsigned not null, product_name varchar(30) not null, price float not null, primary key(id), constraint product_store foreign key (store_id) references store(id));Query OK, 0 rows affected (0.02 sec)
多对多（产品可以在许多商店中使用）
create table store( id int unsigned not null auto_increment, store_name varchar(30) not null, primary key(id));Query OK, 0 rows affected (0.04 sec)create table product( id int unsigned not null auto_increment, store_id int unsigned not null, product_name varchar(30) not null, price float not null, primary key(id));Query OK, 0 rows affected (0.01 sec)create table product_store ( product_id int unsigned not null, store_id int unsigned not null, ConSTRAINT product_store_store foreign key (store_id) references store(id), ConSTRAINT product_store_product foreign key (product_id) references product(id), ConSTRAINT product_store_unique UNIQUE (product_id, store_id))Query OK, 0 rows affected (0.02 sec)
