Enable/Disable/Validate/Novalidate

Enable/Disable/Validate/Novalidate


Enable/Disable/Validate/Novalidate几个关键字对Constraint的控制。
PHP code:
Enable/Disable/Validate/Novalidate
2007/06/25
一、组合特性说明：
是否要求满足约束 Validate Novalidate
已有记录 新增/修改记录 已有记录 新增/修改记录
Enable Yes　 　Yes No　 Yes
Disable Yes　 No No No

Validate确保已有数据符合约束；
Novalidate不必考虑已有数据是否符合约束。

除非Novalidate被指定，Enable默认Validate；
除非Validate被指定，Disable默认Novalidate；
Validate和Novalidate对Enable和Disable没有任何默认暗示。

Enable Validate与Enable相同，检查已有记录和新增记录，确保都符合约束；
Enable Novalidate 允许已有记录不必满足约束条件，但新增/修改的记录必须满足；
Disable Validate禁用约束，删除约束上的索引，不允许修改任何被约束的记录；
Disable Novalidate与Disable相同，禁用约束，删除约束上的索引，且允许修改被约束的记录。

Alter table table_name
Enable/Disable [Validate/Novalidate] constraint constraint_name;

Alter table table_name
Modify constraint constraint_name
Enable/Disable/Validate/Novalidate/
Enable Validate/Enable Novalidate/Disable Validate/Disable Novalidate;

Alter table table_name -----错误语法
Validate/Novalidate constraint constraint_name; -----Alter table不能直接指定Validate/Novalidate
注：以上为Check约束语法，不同的约束类型语法不尽相同，请自行分析。




二、EG：
-------------------------------------------------------------------------------------------
SQL> create table test(id int,name varchar2(10));

Table created.

SQL> alter table test
2 add constraint ck_id check(id>10);

Table altered.
-------------------------------------------------------------------------------------------

测试一：Enable Validate
-------------------------------------------------------------------------------------------
SQL> Alter table test
2 Enable validate constraint ck_id;

Table altered.

SQL> insert into test values(5,’Oracle’);
insert into test values(5,’Oracle’)
*
ERROR at line 1:
ORA-02290: check constraint (EWORM.CK_ID) violated

SQL> insert into test values(17,’ERP’);

1 row created.
-------------------------------------------------------------------------------------------

测试二：Enable Novalidate
-------------------------------------------------------------------------------------------
SQL> alter table test
2 disable constraint ck_id;

Table altered.

SQL> insert into test values(5,’Oracle’);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from test;

ID NAME
---------- ----------
17 ERP
5 Oracle

2 rows selected.

SQL> alter table test
2 enable novalidate constraint ck_id;

Table altered.

SQL> insert into test values(32,’SAP’);

1 row created.

SQL> insert into test values(3,’Linux’);
insert into test values(3,’Linux’)
*
ERROR at line 1:
ORA-02290: check constraint (EWORM.CK_ID) violated
-------------------------------------------------------------------------------------------

测试三：Disable Validate
-------------------------------------------------------------------------------------------
SQL> delete from test where id<10;

2 rows deleted.

SQL> commit;

Commit complete.

SQL> alter table test
2 disable validate constraint ck_id;

Table altered.

SQL> select * from test;

ID NAME
---------- ----------
17 ERP
32 SAP
13 Windows

3 rows selected.

SQL> update test set name=’Change’ where id=17;
update test set name=’Change’ where id=17
*
ERROR at line 1:
ORA-25128: No insert/update/delete on table with constraint (EWORM.CK_ID)
disabled and validated
-------------------------------------------------------------------------------------------

测试四：Disable Novalidate
-------------------------------------------------------------------------------------------
SQL> alter table test
2 disable novalidate constraint ck_id;

Table altered.

SQL> insert into test values(2,’Linux’);

1 row created.

SQL> insert into test values(13,’Windows’);

1 row created.

SQL> update test set name = ’Change’ where id=17;

1 row updated.

SQL> commit;

Commit complete.

SQL> select * from test;

ID NAME
---------- ----------
17 Change
5 Oracle
32 SAP
2 Linux
13 Windows

5 rows selected.
-------------------------------------------------------------------------------------------

本文转自
http://www.itpub.net/thread-800518-1-1.html