Creating References to Objects with REF

You can create views using a REF modifier to get references to objects.

Example 6-7 Query References to Objects with REF

-- Requires Ex. 6-2, Ex. 6-4, and Ex. 6-6
CREATE OR REPLACE VIEW emp_view OF emp_t WITH OBJECT IDENTIFIER(empno)
   AS SELECT e.empno, e.empname, e.salary, REF(d)
         FROM emp e, dept_view d
          WHERE e.deptno = d.deptno;

In Example 6-7, the dept_view joins the emp table on the deptno key.

The advantage of using the MAKE_REF operator, as in Example 6-6, instead of the REF modifier is that with the former, you can create circular references. For example, you can create an employee view that has a reference to the employee's department, while the department view has a list of references to the employees who work in that department.