jastar的专栏

1. 修改redo log file大小SQL> select group#,status from v$log;SQL> alter database add logfile group 4 F:/oracle/product/10.2.0/oradata/orcl/REDO04.LOG size 512m;SQL> alter system switch logfile;S

最近在倒腾Oracle，把EM给搞挂了，害我又得重新弄半天。1. emca -deconfig dbcontrol db进行查询2. emca -repos drop删除repository如果删除错误，手动执行删除相关用户和权限SQL> drop user sysman cascade; SQL> drop role MGMT_USER;SQL> drop user MGMT_VIEW cascade;SQL> drop public synonym MGMT_TARGET_BLA

-- 创建表Create table T1(GroupId int, Keys varchar(2));-- 准备数据insert into T1 values(3, 'a');insert into T1 values(3, 'b');insert into T1 values(3, 'd');insert into T1 values(4, 'a');insert into T1 values(4, 'b');insert into T1 values(5, 'a');i

<br />客户端sqlplus和plsql developer连接集群数据库时时常会有ORA-12545错误，几率很高。据称是Oracle的bug。可以通过修改服务器rac1和rac2的数据库初始化参数来解决这个问题。<br />SQL> sqlplus sys/***@orcl1 as sysdba;<br />SQL> alter system set local_listener='(ADDRESS = (PROTOCOL = TCP)(HOST = 172.168.0.2) (PORT = 152

<br />这样才可以体现出Oracle集群的价值<br />jdbc:oracle:thin:@(DESCRIPTION =<br />        (ADDRESS_LIST =<br />                 (ADDRESS = (PROTOCOL = TCP)(HOST = 172.16.0.1)(PORT = 1521))<br />                 (ADDRESS = (PROTOCOL = TCP)(HOST = 172.16.0.2)(PORT

select to_date('2010-01-01', 'yyyy-mm-dd') + (rownum -1 ) as dates from ALL_OBJECTSwhere to_date('2010-01-01', 'yyyy-mm-dd') + (rownum -1 ) 表All_Objects可以是任意一张表，但是要确保此表的行数不能少于2010-01-01 ~ 2015-12-31这个日期区间的天数，否则日期将不完整，为什么？你懂的。

<br />今天优化一个查询语句：<br />select to_char(m_date, 'MM'), count(*) from m_table group by to_char(m_date, 'MM'), 速度比较慢，需要1.5s左右的时间。在群里面讨教了一下高手，说通过函数索引可以优化, 于是：<br />create index m_date_month on m_table (to_char(m_date, 'MM'));<br />执行查询，<br />select to_char(m_da