使用 ENABLE VALIDATE 选项激活约束时，如果已存在数据不满足约束规则，则会提示错误信息，并且激活约束会失败。此时必须对已存在 数据进行修正，已确保这些数据全部满嘴约束规则。具体方法如下：
（1）建立EXCEPTIONS 表
05:02:44 SQL> @$ORACLE_HOME/rdbms/admin/utlexcpt;
Table created.
05:05:33 SQL> alter table t1
05:06:26 2 add constraint pk_id primary key(deptno);
Table altered.
05:07:04 SQL> select constraint_name,constraint_type,status,table_name from user_constraints
05:07:14 2 where table_name='T1';
CONSTRAINT_NAME C STATUS TABLE_NAME
------------------------------ - -------- ------------------------------
PK_ID P ENABLED T1
U_NAME U ENABLED T1
05:07:17 SQL> alter table t1
05:07:29 2 disable novalidate primary key;
Table altered.
05:07:53 SQL> select constraint_name,constraint_type,status,table_name from user_constraints
05:07:57 2 where table_name='T1';
CONSTRAINT_NAME C STATUS TABLE_NAME
------------------------------ - -------- ------------------------------
PK_ID P DISABLED T1
U_NAME U ENABLED T1
05:08:24 SQL> insert into t1 values (10,'Oracle','BeiJing');
1 row created.
05:09:00 SQL> insert into t1 values (20,'Cuug','BeiJing');
1 row created.
05:09:15 SQL> select * from t1;
DEPTNO NAME LOC
---------- -------------------- --------------------
10 Cisco BeiJing
20 C%ommd ShangHai
30 Commd ShangHai
40 Microsoft ShangHai
10 Oracle BeiJing
20 Cuug BeiJing
6 rows selected.
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（2）激活约束
05:09:52 SQL> alter table t1
05:09:54 2 enable validate primary key exceptions into exceptions;
alter table t1
*
ERROR at line 1:
ORA-02437: cannot validate (SCOTT.PK_ID) - primary key violated
（3）确定不满足约束规则的行
05:12:19 SQL> select deptno ,rowid from t1
05:12:21 2 where rowid in (select row_id from exceptions) for update;
DEPTNO ROWID
---------- ------------------
10 AAANQPAAEAAAAHEAAA
20 AAANQPAAEAAAAHFAAA
10 AAANQPAAEAAAAHHAAB
20 AAANQPAAEAAAAHHAAC
（4）修正数据
05:13:49 SQL> select deptno from t1;
DEPTNO
----------
10
20
30
40
10
20
6 rows selected.
05:13:51 SQL> update t1 set deptno=50 where rowid='AAANQPAAEAAAAHHAAB';
1 row updated.
05:14:27 SQL> update t1 set deptno=60 where rowid='AAANQPAAEAAAAHHAAC';
1 row updated.
05:14:43 SQL> select deptno from t1;
DEPTNO
----------
10
20
30
40
50
60
6 rows selected.
（5）激活约束
05:15:44 SQL> alter table t1
05:15:45 2 enable validate primary key ;
Table altered.