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
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.
As with synthesized objects, you can also select persistently stored references as view columns and use them seamlessly in queries. However, the object references to view objects cannot be stored persistently.