在已建好的table上添加primary key
1.建立索引
create index test_idx
on test(id);
2.添加約束
alter table test
add constraint test_pk primary key (id)
using index test_idx;

在SQLPLUS中登陸時出現以下錯誤
ERROR:
ORA-12638: Credential retrieval failed
解決方法:修改sqlnet.ora
如果SQLNET.AUTHENTICATION_SERVICES= (NTS)一行沒有被注釋,則注釋掉
#SQLNET.AUTHENTICATION_SERVICES= (NTS)
反之取消注釋

ALTER SYSTEM SET EVENTS='10231 trace name context forever,level 10' ;
内部事件，设置在全表扫描时跳过损坏的数据块.

查看tablespace的空間使用情況
select a.tablespace_name,
trunc(sum(b.bytes/1024/1024),2) "FREE(M)",
trunc(sum(a.bytes/1024/1024)-sum(b.bytes/1024/1024),2) "USED(M)",
trunc(sum(a.bytes/1024/1024),2) "ALL(M)",
trunc(sum(b.bytes/1024/1024)/sum(a.bytes/1024/1024),2)*100'%' "Free(%)"
from dba_data_files a
join dba_free_space b
on(a.file_id=b.file_id)
group by a.tablespace_name;

如何指定tnsname.ora的位置
設置環境變量TNS_ADMIN

獲取當前SCN(9i以後)
select dbms_flashback.get_system_change_number from dual;

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