I am rather confused by the hurt-mongering here.
I know how to do them, see below, but no idea why? What are they for?
create table orders (order_no int not null auto_increment, FK_cust_no int not null,
foreign key(FK_cust_no) references customer(cust_no), primary key(order_no)) type=InnoDB;
create table orders (order_no int not null auto_increment, FK_cust_no int not null,
foreign key(FK_cust_no) references customer(cust_no), primary key(order_no));
InnoDB is a storage engine in MySQL. There are quite a few of them, and they all have their pros and cons. InnoDB's greatest strengths are: