MYSQL如何添加多个外键？

create table Employee
(
ssn INTEGER not null unique,
Name varchar(30) not null,
    Address varchar(30) not null,
    Age INTEGER not null,
Sex varchar(10) not null,
Position varchar(20) not null,
    primary key(ssn)
)ENGINE=InnoDB;


create table Department
(
DId INTEGER not null unique,
    Dname varchar(15) not null,
ManagerId INTEGER not null unique,
    primary key(DId)
);
create table Works_In
(
ssn INTEGER not null unique,
DId INTEGER not null unique,
since varchar(15) not null,
primary key(ssn,DId),
FOREIGN KEY(ssn,DId) REFERENCES Employee(ssn) ON DELETE CASCADE ON UPDATE CASCADE
FOREIGN KEY(DId) REFERENCES Department(DId) ON DELETE CASCADE ON UPDATE CASCADE为什么
)ENGINE=InnoDB;
在Works_In中给Employee和Department加两个外键
这样为什么不行？
ERROR 1005 (HY000) at line 62: Can't create table './HumanResources/Works_In.frm' (errno: 150)
应该怎么样写？

---

主键是唯一的，不能用两个的吧, 而且要非空。

主键不能做外键使用！！

楼主缺乏sql的基础知识，建议去mysql网站上看看。

---

create table Employee
(
ssn INTEGER not null unique,
Name varchar(30) not null,
    Addre