看起来 MySQL 接受它(不抱怨语法)，但实际上并没有创建外键.

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

要创建这个外键，运行这个命令:

To create this foreign key, run this command:

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