從Oracle9i開始，Oracle答應對于視圖(view)進行主鍵、唯一鍵、外鍵約束的聲名。NOT NULL約束可以從基表繼續，所以不答應顯示聲明。
由于視圖約束僅僅是聲明而已，所以其狀態只能是DISABLE NOVALIDATE。以下是一個簡單范例說明:
SQL> CREATE VIEW d10_emp
2 ( empno, ename, job,deptno,
3 CONSTRAINT pk_d10
4 PRIMARY KEY (ename)
5 RELY DISABLE NOVALIDATE
6 ) AS
7 SELECT empno, ename, job ,deptno
8 FROM emp
9 WHERE deptno = 10; View created.SQL> select * from d10_emp; EMPNO ENAME JOB DEPTNO
---------- ---------- --------- ----------
7782 CLARK MANAGER 10
7839 KING PRESIDENT 10
7934 MILLER CLERK 10SQL> select CONSTRAINT_NAME,TABLE_NAME,CONSTRAINT_TYPE from user_constraints
2 where table_name='D10_EMP';CONSTRAINT_NAME TABLE_NAME C
------------------------------ ------------------------------ -
PK_D10 D10_EMP P 由于此約束僅僅為"約束聲明",所以不具有實際約束力:SQL> insert into d10_emp values(7777,'EYGLE','MANAGER',10);1 row created.SQL> insert into d10_emp values(8888,'EYGLE','MANAGER',10);1 row created.SQL> select * from d10_emp; EMPNO ENAME JOB DEPTNO
---------- ---------- --------- ----------
7782 CLARK MANAGER 10
7839 KING PRESIDENT 10
7934 MILLER CLERK 10
7777 EYGLE MANAGER 10
8888 EYGLE MANAGER 10
-----原文地址：http://www.eygle.com/archives/2006/02/oracle9i_view_constraints_declarative.Html
