t_xiaoxi  order by cid desc) where rownum<10000) where rn>9980) order by cid desc;
执行旉™—´0.03¿U?br />2.按分析函数来åˆ?br />select * from (select t.*,row_number() over(order by cid desc) rk from t_xiaoxi t) where rk<10000 and rk>9980;
执行旉™—´1.01¿U?br />3.按ROWNUM来分
select * from(select t.*,rownum rn from(select * from t_xiaoxi order by cid desc) t where rownum<10000) where

rn>9980;执行旉™—´0.1¿U?br />其中t_xiaoxiä¸ø™¡¨åç§°åQŒcidä¸ø™¡¨çš„关键字ŒDµï¼Œå–按CID降序排序后的½W?981-9999条记录，t_xiaoxi表有70000多条记录
个äh感觉1的效率最好，3‹Æ¡ä¹‹åQ?最å·?/p>

PRAGMA AUTONOMOUS_TRANSACTION中文¾˜»è¯‘˜q‡æ¥å?#8220;自治事务”åQˆç¿»è¯‘çš„˜q˜ç®—好理解）åQŒå¯¹äºŽå®šä¹‰æˆè‡ªæ²»äº‹åŠ¡çš„ProcedureåQŒå®žé™…上相当于一ŒD늋¬ç«‹è¿è¡Œçš„½E‹åºŒDµï¼Œ˜q™æ®µ½E‹åºä¸ä¾èµ–于ä¸È¨‹åºï¼Œä¹?strong>不干æ¶?/strong>ä¸È¨‹åº?/p>

自治事务的特�/h2>

½W¬ä¸€,˜q™æ®µ½E‹åºä¸ä¾èµ–于原有Main½E‹åºåQŒæ¯”如Main½E‹åºä¸­æœ‰æœªæäº¤çš„数据åQŒé‚£ä¹ˆåœ¨è‡ªæ²»äº‹åŠ¡ä¸­æ˜¯æŸ¥æ‰¾ä¸åˆ°çš„ã€?/p>

½W¬äºŒ,在自æ²ÖMº‹åŠ¡ä¸­åQŒcommit或者rollback只会提交或回滚当前自æ²ÖMº‹åŠ¡ä¸­çš„DMLåQŒä¸ä¼šåª„响到Main½E‹åºä¸­çš„DMLã€?/p>

Autonomous Transaction Demo 1

Without Pragma Autonomous Transaction

With Pragma Autonomous Transaction

Autonomous Transaction Demo 2

CREATE OR REPLACE FUNCTION howmanyrows RETURN INTEGER IS
 i INTEGER;

 PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
  SELECT COUNT(*)
  INTO i
  FROM t;

  RETURN i;
END howmanyrows;
/

-- empty the test table
TRUNCATE TABLE t;

exec testproc;

pl/sql中设¾|?

tools->preferences->sql window->AutoSelect statement

然后光标攑֜¨ä¸€è¡Œï¼ŒæŒ‰F8ž®±å¯ä»¥äº†, æ³¨æ„: æ¯ä¸ªè¯­å¥¾l“å°¾˜q˜è¦åˆ†å·æ ‡æ³¨ä¸€ä¸‹ï¼

package com.abin.wto.dbs.oracle;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import oracle.sql.CLOB;

public class OperateOracle {
 public static void main(String[] args) {
  Connection conn=null;
  PreparedStatement ps=null;
  ResultSet rs=null;
  try {
   Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
   String url="jdbc:oracle:thin:@localhost:1521:XE";
   conn=DriverManager.getConnection(url,"abin","abin");
   String sql="insert into bignumber values(?,?)";
   ps=conn.prepareStatement(sql);
   ps.setInt(1, 8888);
   java.sql.Clob  clob=oracle.sql.CLOB.createTemporary(conn, false, oracle.sql.CLOB.DURATION_SESSION);
   clob.setString(1, "55555555555555");
   ps.setClob(2, clob);
   int result=ps.executeUpdate();
   System.out.println("result="+result);
  } catch (Exception e) {
   e.printStackTrace();
  }finally{
   if(ps!=null){
    try {
     ps.close();
    } catch (SQLException e) {
     e.printStackTrace();
    }
   }
   try {
    CLOB.freeTemporary(null);
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }

}

SQL> show parameter processes

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
aq_tm_processes                      integer     1
db_writer_processes                  integer     1
job_queue_processes                  integer     10
log_archive_max_processes            integer     2
processes                            integer     150

SQL> show parameter sessions

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
java_max_sessionspace_size           integer     0
java_soft_sessionspace_limit         integer     0
license_max_sessions                 integer     0
license_sessions_warning             integer     0
logmnr_max_persistent_sessions       integer     1
mts_sessions                         integer     165
sessions                             integer     170
shared_server_sessions               integer     165
SQL>

2. 修改processes和sessions�/p>

SQL> alter system set processes=300 scope=spfile;

¾pȝ»Ÿå·²æ›´æ”V€?/p>

SQL> alter system set sessions=335 scope=spfile;

¾pȝ»Ÿå·²æ›´æ”V€?/p>

3. 修改processeså’Œsessions值必™å»é‡å¯oracle服务器才能生æ•?/p>

ORACLE的连接数(sessions)与其参数文äšg中的˜q›ç¨‹æ•?process)有关åQŒå®ƒä»¬çš„关系如下åQ?/p>

sessions=(1.1*process+5)

　查询数据库当前进½E‹çš„˜qžæŽ¥æ•ŽÍ¼š

　select count(*) from v$process;

　　查看数据库当前会话的˜qžæŽ¥æ•ŽÍ¼š

　　select count(*) from v$session;

　　查看数据库的òq¶å‘˜qžæŽ¥æ•ŽÍ¼š

　　select count(*) from v$session where status='ACTIVE';

　　查看当前数据库徏立的会话情况åQ?/p>

　　select sid,serial#,username,program,machine,status from v$session;

　查询数据库允许的最大连接数åQ?/p>

　　select value from v$parameter where name = 'processes';

　　或者：show parameter processes;

　　修改数据库允许的最大连接数åQ?/p>

　　alter system set processes = 300 scope = spfile;

　　(需要重启数据库才能实现˜qžæŽ¥æ•°çš„修改)

　　重启数据库：

　　shutdown immediate;

　　startup;

　　查看当前有哪些用æˆäh­£åœ¨ä‹É用数据：

　　select osuser,a.username,cpu_time/executions/1000000||'s',sql_fulltext,machine

　　from v$session a,v$sqlarea b

　　where a.sql_address = b.address

　　order by cpu_time/executions desc;

　　备注åQšUNIX 1个用户session对应一个操作系¾lŸprocessåQŒè€ŒWindows体现在线½E‹ã€?/p>

　　启动oracle

　　su - oracle

　　sqlplus system/pwd as sysdba   //˜q›å…¥sql

　　startup                                      //启动数据åº?/p>

　　lsnrctl start                               //启动监听

　　sqlplus "/as sysdba"

　　shutdown immediate;

　　startup mount;

　　alter database open;