Oracle 如何在超类型表中定义子类型列的范围？

我使用一个超类型表来包含超类型和子类型的所有数据。但我不知道如何定义子类型的引用列的范围

例如：

CREATE OR REPLACE TYPE PersonObj AS OBJECT(
oid integer,
id integer,
name varchar(20),
street varchar(20),
city varchar(10),
state varchar(20),
zipcode varchar(5),
birthDate date,
kidNames set_kids,
picture varchar(100),
place LocationAdt
) NOT FINAL;
/

CREATE OR REPLACE TYPE StudentObj UNDER PersonObj (
studentId varchar(10),
major REF DepartmentObj,
advisor REF ProfessorObj,
hasTaken set_ref_enrolledobj);
/

我想这样定义范围：

CREATE TABLE person OF personobj (id PRIMARY KEY,
major SCOPE IS department, 
advisor SCOPE IS professor) 
OBJECT IDENTIFIER IS PRIMARY KEY 
NESTED TABLE kidNames STORE AS student_kidnames, 
NESTED TABLE hastaken STORE AS student_hastaken;

但它返回错误ORA-00904：“主要”：无效标识符

如何在超类型表中描述子类型的引用列的范围？ 创建了表部门和教授

更多信息：

CREATE TABLE student OF studentobj (id PRIMARY KEY,
major SCOPE IS department, 
advisor SCOPE IS professor) 
OBJECT IDENTIFIER IS PRIMARY KEY 
NESTED TABLE kidNames STORE AS student_kidnames, 
NESTED TABLE hastaken STORE AS student_hastaken;

上面的命令是成功的

谢谢你提供的任何信息