请问创建外键的sql语句

Sys_Employee表
eid  ePosition

Sys_DicPosition表
id  PositionName

alter table Sys_Employee
add constraint
foreign key(ePosition) references Sys_DicPosition(id)

我的代码如上，提示foreign附近语法错误，请问怎么改？

---

alter table Sys_Employee
add constraint fk_id-- 加一个约束名
foreign key(ePosition) references Sys_DicPosition(id)

---

SQL code:
alter table Sys_Employee
add constraint FK_ePosition
foreign key(ePosition) references Sys_DicPosition(id)

---

alter table Sys_Employee
add constraint FK_ePosition-加个约束名
foreign key(ePosition) references Sys_DicPosition(id)

---

alter table Sys_Employee
add constraint 约束名_NAME
foreign key(ePosition) references Sys_DicPosition(id)

< table_constraint > ::=
  [ CONSTRAINT constraint_name ]
    { [ { PRIMARY KEY | UNIQUE }
        [ CLUSTERED | NONCLUSTERED ]
        { ( column [ ,...n ] ) }
        [ WITH FILLFACTOR = fillfactor ]
        [ ON { filegroup | DEFAULT } ]
        ]
        |    FOREIGN KEY
        &