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这ALTER TABLE是我在过程中发现的代码的范围
create type employee_type AS OBJECT
(empno number(4),
ename varchar2(40),
dept_ref REF department_type)
/
create table employee of employee_type
(empno PRIMARY KEY)
/
create type department_type AS OBJECT
(deptno number(2),
dname varchar2(20),
loc varchar(20))
/
create table employee of employee_type
(empno PRIMARY KEY)
/
create table department of department_type
(deptno PRIMARY KEY)
/
alter table employee
add (scope for (dept_ref) is department)
/
我不明白为什么我们需要改变员工表中添加范围为到部门表,我的意思是dept_ref已转交department_type已经和department表由department_type对象组成,那么add scope statment是做什么的?
除非示例来自作业,在这种情况下,它总是COURSES和STUDENTS :) – APC