eygle老师的一些小文章

来源：互联网发布：多线程数据共享编辑：程序博客网时间：2024/04/29 17:28

本文是完全转自eygle老师的，目的是为了自己学习，绝无他用。如果涉及侵权问题，请联系我删除，我会在文章中注明原文链接。。。

1、如何在其他Session跳过被锁定的记录

原文链接：http://www.eygle.com/archives/2005/03/eciouaeeeusessi.html

有人问到这样的问题:如果一个用户对记录加锁，如何使其他用户看不到这条记录。
此前并未注意到这样一个用法（需要8.1.7.4.16以上的版本支持）:

[oracle@jumper oracle]$ sqlplus scott/tigerSQL*Plus: Release 9.2.0.4.0 - Production on Fri Mar 4 11:59:46 2005Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.Connected to:Oracle9i Enterprise Edition Release 9.2.0.4.0 - ProductionWith the Partitioning optionJServer Release 9.2.0.4.0 - ProductionSQL> select * from dept;    DEPTNO DNAME          LOC---------- -------------- -------------        10 ACCOUNTING     NEW YORK        20 RESEARCH       DALLAS        30 SALES          CHICAGO        40 OPERATIONS     BOSTON        33 ORACLE         beijing        35 Oracle         Beijing        36 Oracle         Beijing        37 Oracle         Beijing8 rows selected.SQL> select * from dept where  deptno =10 for update;    DEPTNO DNAME          LOC---------- -------------- -------------        10 ACCOUNTING     NEW YORKSQL> ![oracle@jumper oracle]$ sqlplus scott/tigerSQL*Plus: Release 9.2.0.4.0 - Production on Fri Mar 4 12:00:14 2005Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.Connected to:Oracle9i Enterprise Edition Release 9.2.0.4.0 - ProductionWith the Partitioning optionJServer Release 9.2.0.4.0 - ProductionSQL> select * from dept for update skip locked;    DEPTNO DNAME          LOC---------- -------------- -------------        20 RESEARCH       DALLAS        30 SALES          CHICAGO        40 OPERATIONS     BOSTON        33 ORACLE         beijing        35 Oracle         Beijing        36 Oracle         Beijing        37 Oracle         Beijing7 rows selected.SQL>

2、使用SET TRANSACTION给事务命名

原文链接：http://www.eygle.com/archives/2005/03/eoaset_transact.html

以前没有注意的命令，可以使用SET TRANSACTION给事务命名。
v$transaction中的name字段代表的正是:Name of a named transaction。

[oracle@jumper bdump]$ sqlplus "/ as sysdba"SQL*Plus: Release 9.2.0.4.0 - Production on Mon Mar 14 23:17:21 2005Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.Connected to:Oracle9i Enterprise Edition Release 9.2.0.4.0 - ProductionWith the Partitioning optionJServer Release 9.2.0.4.0 - ProductionSQL> set transaction name 'Update Dept Table';Transaction set.SQL> select * from scott.dept;    DEPTNO DNAME          LOC---------- -------------- -------------        10 ACCOUNTING     NEW YORK        20 RESEARCH       DALLAS        30 SALES          CHICAGO        40 OPERATIONS     BOSTON        33 ORACLE         Beijing        35 Oracle         Beijing        36 Oracle         Beijing        37 Oracle         Beijing8 rows selected.SQL> update scott.dept set LOC='Home' where deptno=35;1 row updated.SQL> select xidusn,xidslot,xidsqn,used_ublk,used_urec,name from v$transaction;  XIDUSN    XIDSLOT     XIDSQN  USED_UBLK  USED_UREC           NAME---------- ---------- ---------- ---------- ---------- --------------------   3         17        9120          1        1         Update Dept Table

要注意，必须是事务开始之前，如果已经开始了事务，但是没有提交（也就是还没有完成）这样就不能再给事务命名了。