MySQL Syntax in creating Foreign Key

问题

Is this syntax correct in creating a Foreign Key?

create table department
(
  departmentID int not null auto_increment primary key,
  name varchar(30)
) type=InnoDB;

create table employee
(
  employeeID int not null auto_increment primary key,
  name varchar(80),
  job varchar(30),
  departmentID int not null references department(departmentID)
) type=InnoDB;

回答1:

It looks like MySQL accepts it (doesn't complain about the syntax) but the foreign key is not actually created.

To create this foreign key, run this command:

ALTER TABLE employee ADD CONSTRAINT fk_department FOREIGN KEY (departmentID) REFERENCES department (departmentID);

回答2:

create table employee
(
  employeeID int not null auto_increment primary key,
  name varchar(80),
  job varchar(30),
  departmentID int not null ADD CONSTRAINT fk_department FOREIGN KEY (departmentID) references department(departmentID)
) 

回答3:

FOREIGN KEY (departmentID) REFERENCES department(departmentID)

Thanks.!

来源：https://stackoverflow.com/questions/6977086/mysql-syntax-in-creating-foreign-key