摘要： ThreadLocal模式是为了解决多线程程序中，数据共享的问题，ThreadLocal模式贯穿了整个Struts2和Xwork框架。 阅读全文

摘要： 进程:它是程序的一次动态执行过程，它需要经历从代码加载，到代码执行，到执行完毕的一个完整过程，这个过程也是进程从产生、发展到最终消亡的过程。线程:线程是比进程更小的执行单位，它是在进程的基础上进一步划分，所谓多线程，是指一个进程在执行的过程可以产生多个更小的程序单元，这些更小的单元-称为线程。这些线程可以同时存在，同时运行，一个进程可能产生多个同时执行的线程。----------java中进程的实现：1、继承Thread类实现多线程: 1 package com.dyj.test; 2 3 public class TestThread extends Thread { 4 5 p... 阅读全文

摘要： Oracle 修改表的限制 To make a NOT NULL column nullable, use the alter table command with the NULL clause,as follows:alter table TROUBLE modify(Condition NULL);The Rules for Adding or Modifying a ColumnThese are the rules for modifying a column: (在任何情况下) 1、You can increase a character column’s wi... 阅读全文

摘要： http://orafaq.com/node/854ORACLE锁: Oracle uses locks to control concurrent access to data. A lock gives you temporary ownership of a database resource such as a table or row of data. Thus, data cannot be changed by other users until you finish with it. You need never explicitly lock a resource becau 阅读全文

摘要： 注意:国际通用的日期中；周末才是一个周的第一天ROUND and TRUNC Date Functionsnext lists the format models you can use with the ROUND and TRUNC date functions and the units to which they round and truncate dates. The default model, 'DD', returns the date rounded or truncated to the day with a time of midnight.Date F 阅读全文

摘要： CASE expression perform if-then-else logic in SQL without having to use PL/SQL.CASE works in a similar manner to DECODE().CASE is ANSI-compliant.There are two types of CASE expressions: Simple case expressions use expressions to determine the returned value. Searched case expressions use condi... 阅读全文