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bitand　　bitand 　　返回两个数值型数值在按位进行 AND 运算后的结果。 　　语法 　　BITAND(nExpression1, nExpression2) 　　参数 　　nExpression1, nExpression2 　　指定按位进行 AND ...

http://blog.csdn.net/hijk139/article/details/7411106 小结:经加大alter table x allocate(extent 1000m);通过监控select * from v$session_wait;--仍会产生hw contention 明天继续分析! ...

SQL> alter table t_free storage (maxextents 120);alter table t_free storage (maxextents 120)*第 1 行出现错误:ORA-25150: 不允许对区参数执行 ALTERING SQL> select tablespace_name,extent_mana...

http://blog.csdn.net/gguxxing008/article/details/6858579

http://docs.oracle.com/cd/E11882_01/server.112/e25513/waitevents003.htm#sthref3925

Table 10-1 Wait Events and Potential CausesWait EventGeneral AreaPossible CausesLook for / Examinebuffer busy waitsBuffer cache, DBWRDepends on buffer type. For example, waits for an index blo...

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http://www.itpub.net/thread-1088598-1-1.html

Diff B/W Truncate & DeleteSubmitted by arunbharat2001 on Sat, 2012-10-20 11:03SQL & PL/SQLDelete 1.DML data can be recovered by rollback before commit2.Remove any subset of data3.Delete is slo...

http://qjoycn.iteye.com/blog/1279731

有个简单方法，用(length(str1) - length(replace(str1, str2)))/length(str2)应该能给出str2在str1中出现的次数。select (length('xyzabc123abcefgh') - length(replace('xyzabc123abcefgh', 'abc')))/leng...

SQL> insert into t_date values(null); 1 row inserted SQL> commit; Commit complete SQL> select to_char(a,'yyyymmdd') from t_date; TO_CHAR(A,'YYYYMMDD')-----------------...

1,SQL> create table t1(a int,b int);表已创建。SQL> create table t2(a int,b int);表已创建。SQL> insert into t1 select level,level from dual connect by level<已创建1999999行。SQL> commit;提交完...

http://www.orafaq.com/node/758

oracle 动态采样 1,动态采样就是为了提升数据库的性能,通过对表和其索引的谓词选择度和统计收集更加精确的信息. 2,上述的表及索引的统计包括:表的数据块数,索引数据块数,表的基数,关联列的统计.&n...

SQL> show parameter optimizer_dynamic_samNAME                        &nb...

unnest 1,这个提示会让优化器在评估访问路径和连接操作时,会考虑把把子查询整合到包含它的语句之中, 2,在子查询被整合或合并之前,优化器先要验证语句是否合理,必须通过启发式或查询验证 use_...

oracle hint parallel    1,并行度如合理,启用   2,并行度如不合同不启用   3,default,启用默认参数的配置值SQL> create table t_parallel(a int) parallel 2;表已创建...

pq_distribute hint1,/*+ pq_distribute(@查询块 外部分发表 内部分发表) */2,此提示让优化器在生产和消费查询服务器分发两个连接表的记录集,这种分发可以极大提升并行连接操作的性能3,6种分发提示的组合用...

SQL> create table t_partition(partion_id int,a int)  2  partition by range(partition_id)  3  (  4   partition p1 values less than (10) tablespace users ...