(ZZ)Oracle约束的关键字Enable/Disable/Validate/Novalidate

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1 组合特性说明

	Validate	Novalidate
已有记录	新增/删除记录	已有记录	新增/删除记录
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。
 
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。
2 建表
SQL> create table test(id int, name varchar2(10));
Table created
SQL> alter table test add constraint ck_id check(id > 10);
Table altered
3 测试1: Enable Validate
SQL> alter table test Enable validate constraint ck_id;
Table altered
SQL> insert into test values(5, 'Oracle');
insert into test values(5, 'Oracle')
ORA-02290: 违反检查约束条件 (MYHR.CK_ID)
SQL> insert into test values(17,'ERP');
1 row inserted
SQL> commit;
Commit complete
4 测试2: Enable Novalidate
SQL> alter table test disable constraint ck_id;
Table altered
SQL> insert into test values(5, 'Oracle');
1 row inserted
SQL> commit;
Commit complete
SQL> select * from test;
           ID NAME
----------- ----------
          17 ERP
            5 Oracle
 
SQL> alter table test enable novalidate constraint ck_id;
Table altered
SQL> insert into test values(32, 'SAP');
1 row inserted
SQL> insert into test values(3, 'Linux');
insert into test values(3, 'Linux')
ORA-02290: 违反检查约束条件 (MYHR.CK_ID)
SQL> commit;
Commit complete
5 测试3: Disable Validate
SQL> delete from test where id < 10;
1 row deleted
SQL> commit;
Commit complete
SQL> alter table test disable validate constraint ck_id;
Table altered
SQL> select * from test;
             ID NAME
------------- ----------
             17 ERP
             32 SAP
SQL> update test set name = 'Change' where id = 17;
update test set name = 'Change' where id = 17
ORA-25128: 不能对带有禁用和验证约束条件 (MYHR.CK_ID) 的表进行插入/更新/删除
6 测试4: Disable Novalidate
SQL> alter table test disable novalidate constraint ck_id;
Table altered
SQL> insert into test values(2, 'Linux');
1 row inserted
SQL> insert into test values(13, 'Windows');
1 row inserted
SQL> update test set name = 'Change' where id = 17;
1 row updated
SQL> commit;
Commit complete
SQL> select * from test;
          ID NAME
---------- ----------
          17 Change
          13 Windows
          32 SAP
           2 Linux