Oracle约束的4种状态小结

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约束的4种状态：

disable novalidate 既不会约束新增数据也不会验证已有数据，等同于disable

enable novalidate 约束新增数据但不会验证已有数据

disable validate 约束新增数据但不会验证已有数据，启用后禁止DML

enable validate 约束新增数据并验证已有数据，等同于enable

扩展解释：

disable / enable 针对新增数据（对于唯一性约束，enable会自动创建唯一性索引，disable会自动drop索引）；

novalidate / validate 针对已有数据。

测试：

Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.1.0

Connected as system

SQL> drop table dept2;

Table dropped

SQL> create table dept2 as select * from scott.dept;

Table created

SQL> select * from dept2 order by deptno;

DEPTNO DNAME          LOC
------ -------------- -------------
    10 ACCOUNTING     NEW YORK
    20 RESEARCH       DALLAS
    30 SALES          CHICAGO
    40 OPERATIONS     BOSTON

SQL> alter table dept2 add constraint dept2_u1 unique(deptno);

Table altered

SQL> select index_name,table_name,uniqueness from dba_indexes where index_name = 'DEPT2_U1';

INDEX_NAME                     TABLE_NAME                     UNIQUENESS
------------------------------ ------------------------------ ----------
DEPT2_U1                       DEPT2                          UNIQUE

SQL> select constraint_name,status,validated from dba_constraints where constraint_name = 'DEPT2_U1';

CONSTRAINT_NAME                STATUS   VALIDATED
------------------------------ -------- -------------
DEPT2_U1                       ENABLED VALIDATED

SQL> insert into dept2(deptno) values(10);

insert into dept2(deptno) values(10)

ORA-00001: unique constraint (SYSTEM.DEPT2_U1) violated

SQL> select * from dept2 order by deptno;

DEPTNO DNAME          LOC
------ -------------- -------------
    10 ACCOUNTING     NEW YORK
    20 RESEARCH       DALLAS
    30 SALES          CHICAGO
    40 OPERATIONS     BOSTON

SQL> alter table dept2 modify constraint dept2_u1 disable novalidate;

Table altered

SQL> select index_name,table_name,uniqueness from dba_indexes where index_name = 'DEPT2_U1';

INDEX_NAME                     TABLE_NAME                     UNIQUENESS

------------------------------ ------------------------------ ----------

（disable自动移除索引）

SQL> select constraint_name,status,validated from dba_constraints where constraint_name = 'DEPT2_U1';

CONSTRAINT_NAME                STATUS   VALIDATED
------------------------------ -------- -------------
DEPT2_U1                       DISABLED NOT VALIDATED

SQL> insert into dept2(deptno) values(10);

1 row inserted

SQL> select * from dept2 order by deptno;

DEPTNO DNAME          LOC
------ -------------- -------------
    10 ACCOUNTING     NEW YORK
    10
    20 RESEARCH       DALLAS
    30 SALES          CHICAGO
    40 OPERATIONS     BOSTON

SQL> alter table dept2 modify constraint dept2_u1 enable novalidate;

alter table dept2 modify constraint dept2_u1 enable novalidate

ORA-02299: cannot validate (SYSTEM.DEPT2_U1) - duplicate keys found
（因为enable会去创建唯一性索引，而已有数据deptno存在重复数据10，所以这里不能enable）

SQL> delete from dept2 where deptno=10 and dname is null;

1 row deleted

SQL> alter table dept2 modify constraint dept2_u1 enable novalidate;

Table altered

SQL> select index_name,table_name,uniqueness from dba_indexes where index_name = 'DEPT2_U1';

INDEX_NAME                     TABLE_NAME                     UNIQUENESS
------------------------------ ------------------------------ ----------

DEPT2_U1 DEPT2 UNIQUE

（enable会自动创建唯一性索引）

SQL> select constraint_name,status,validated from dba_constraints where constraint_name = 'DEPT2_U1';

CONSTRAINT_NAME                STATUS   VALIDATED
------------------------------ -------- -------------
DEPT2_U1                       ENABLED NOT VALIDATED

SQL> insert into dept2(deptno) values(10);

insert into dept2(deptno) values(10)

ORA-00001: unique constraint (SYSTEM.DEPT2_U1) violated

SQL> alter table dept2 modify constraint dept2_u1 disable validate;

Table altered

SQL> select index_name,table_name,uniqueness from dba_indexes where index_name = 'DEPT2_U1';

INDEX_NAME                     TABLE_NAME                     UNIQUENESS
------------------------------ ------------------------------ ----------

SQL> select constraint_name,status,validated from dba_constraints where constraint_name = 'DEPT2_U1';

CONSTRAINT_NAME                STATUS   VALIDATED
------------------------------ -------- -------------
DEPT2_U1                       DISABLED VALIDATED

SQL> insert into dept2(deptno) values(10);

insert into dept2(deptno) values(10)

ORA-25128: No insert/update/delete on table with constraint (SYSTEM.DEPT2_U1) disabled and validated

（disable validate后禁止DML）

SQL> select * from dept2 order by deptno;

DEPTNO DNAME          LOC
------ -------------- -------------
    10 ACCOUNTING     NEW YORK
    20 RESEARCH       DALLAS
    30 SALES          CHICAGO
    40 OPERATIONS     BOSTON

SQL> alter table dept2 modify constraint dept2_u1 enable validate;

Table altered

SQL> select index_name,table_name,uniqueness from dba_indexes where index_name = 'DEPT2_U1';

INDEX_NAME                     TABLE_NAME                     UNIQUENESS
------------------------------ ------------------------------ ----------
DEPT2_U1                       DEPT2                          UNIQUE

SQL> select constraint_name,status,validated from dba_constraints where constraint_name = 'DEPT2_U1';

CONSTRAINT_NAME                STATUS   VALIDATED
------------------------------ -------- -------------
DEPT2_U1                       ENABLED VALIDATED

SQL> insert into dept2(deptno) values(10);

insert into dept2(deptno) values(10)

ORA-00001: unique constraint (SYSTEM.DEPT2_U1) violated

SQL> select * from dept2 order by deptno;

DEPTNO DNAME          LOC
------ -------------- -------------
    10 ACCOUNTING     NEW YORK
    20 RESEARCH       DALLAS
    30 SALES          CHICAGO
    40 OPERATIONS     BOSTON

SQL>

REF: <<Expert Oracle Database 11g Administration>> Page 308, Integrity Constraint States