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从Oracle9i开始，Oracle允许对于视图(view)进行主键、唯一键、外键约束的声名。NOT NULL约束可以从基表继承，所以不允许显示声明。
由于视图约束仅仅是声明而已，所以其状态只能是DISABLE NOVALIDATE。
以下是一个简单范例说明:
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
由于此约束仅仅为"约束声明",所以不具有实际约束力:
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
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