unique index unusable
/*
*如果是PK的unique index设置为unusable之后将不能向其中插入数据，这样在imp 时使用skip_unusable参数也不起作用，不管数据重复与否都无法
插入表。
*/
SQL> create table test(id int, name varchar2(32));
Table created.
SQL> alter table test add constraint pk_test_id primary key (id);
Table altered.
SQL> insert into test values(1, 'a');
1 row created.
SQL> insert into test values(2, 'b');
1 row created.
SQL> commit;
Commit complete.
SQL> select index_name from user_indexes where table_name = 'TEST';
INDEX_NAME
------------------------------
PK_TEST_ID
SQL> alter index pk_test_id unusable;
Index altered.
SQL> select index_name, status from user_indexes where table_name = 'TEST';
INDEX_NAME STATUS
------------------------------ --------
PK_TEST_ID UNUSABLE
SQL> SELECT * from test;
ID NAME
---------- --------------------------------
1 a
2 b
3 c
4 d
5 e
SQL> insert into test values(5, 'e');
insert into test values(5, 'e')
*
ERROR at line 1:
ORA-01502: index 'ZHF.PK_TEST_ID' or partition of such index is in unusable
state
SQL>
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