win7自动升级到了ie11，但是debug工具太难用了，准备会退到9，但是在添加删除程序里，把ie11的功能关闭，安装9时，提示ie已经安装。
并且ie图标也没了。。progrem files下面的ie启动程序也没了。。。。

最好在这找到了卸载的办法
http://www.iefans.net/windows-7-ie11-wufa-xiezai-chongxin-anzhuang-gengxin-banben/

weblogic.security.SecurityInitializationException: 認証が拒否されました。起動アイデンティティが有効ではありません。起動アイデンティティ・ファイル(boot.properties)のユーザー名またはパスワード(もしくはその双方)が有効ではありません。起動アイデンティティ・ファイルが作成された後に起動アイデンティティが変更されていることが考えられます。適切な値のユーザー名およびパスワードで起動アイデンティティ・ファイルを編集および更新してください。更新された起動アイデンティティ・ファイルを使用して初めてサーバーを起動するときには、それらの値は暗号化されます。
    at weblogic.security.service.CommonSecurityServiceManagerDelegateImpl.doBootAuthorization(CommonSecurityServiceManagerDelegateImpl.java:960)
    at weblogic.security.service.CommonSecurityServiceManagerDelegateImpl.initialize(CommonSecurityServiceManagerDelegateImpl.java:1054)
    at weblogic.security.service.SecurityServiceManager.initialize(SecurityServiceManager.java:873)
    at weblogic.security.SecurityService.start(SecurityService.java:148)
    at weblogic.t3.srvr.SubsystemRequest.run(SubsystemRequest.java:64)
    at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
    at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)
Caused By: javax.security.auth.login.FailedLoginException: [Security:090303]ユーザーweblogicの認証が失敗しました。weblogic.security.providers.authentication.LDAPAtnDelegateException: [Security:090295]予期しない例外が捕捉されました
    at weblogic.security.providers.authentication.LDAPAtnLoginModuleImpl.login(LDAPAtnLoginModuleImpl.java:251)
    at com.bea.common.security.internal.service.LoginModuleWrapper$1.run(LoginModuleWrapper.java:110)
    at java.security.AccessController.doPrivileged(Native Method)

http://bbs.weblogicfans.net/viewthread.php?tid=399&extra=&ordertype=1&page=4

set ADMIN_URL=XXX，竟然用的是计算机名。。。。。。。。。。。

测试机装完环境，配置集群时，为了便于辨认，修改了计算机名，悲剧的根源。。。。。。
然后发现stopManagedWebLogic.cmd里面用的也是计算机名。。。。。。

计算机名，ip都可能被改，我感觉弄个localhost比啥都强，实在不明白这么做得原因是啥。

不过以后搭建环境时，一定要先把系统要修改的做完，然后再装其他软件。

在HP-UX操作系统中使用-d32或-d64来指定使用Java应用程序使用32bit的JVM还是使用64bit的JVM(默认32bit).
一个Java应用程序运行时，它会根据自己所在的HP-UX使用的CPU类型及指定的JVM位数(-d32 or保持默认、-d64)使用$JAVA_HOME/java(壳)自动选择要执行的JVM.

Itanium:
$JAVA_HOME/bin/IA64N/java
$JAVA_HOME/bin/IA64W/java

PA-RISC:
$JAVA_HOME/bin/PA_RISC/java
$JAVA_HOME/bin/PA_RISC2.0/java
$JAVA_HOME/bin/PA_RISC2.0W/java

目录说明
PA_RISC            PA_RISC 1.1 32-bit JVM
PA_RISC2.0       PA-RISC 2.0 32-bit JVM
PA_RISC2.0W     PA-RISC 2.0 64-bit JVM
IA64N      Integrity narrow 32-bit JVM
IA64W     Integrity wide 64-bit JVM

WebLogic Server 8.1及WebLogic Serevr 9.x and later version使用64位JVM.

WebLogic Server 8.1:
修改${Domain_home}下的startWebLogic.sh和startManagedWebLogic.sh中两个脚本的MEM_ARGS参数值，在此参数值的最前面加上-64参数即可，例如:
MEM_ARGS=”-d64 –Xms512m –Xmx1024m…”

WebLogic Serevr 9.x and later version:
修改${Domain_home}/bin/下的setDomainEnv.sh脚本MEM_ARGS参数值，在此参数值的最前面加上-64参数即可。

转载自tdy218's blog

最近的项目涉及到了JAVA需要调用C程序的问题。主要是调用C写的加密算法。
主要解决方案是应用JNI去调用C生成的so库
用eclispe新建一个java project项目,项目名称为spidHandle，注意下面VC的项目名称也是spidHandle，他们分别是用eclispe和VC6.0创建的，不是同个项目。
编写一个JNI入口类SpidHandle.java：


通过CMD命令窗口，CMD命令窗口定位到SpidHandle.java的目录下，编译SpidHandle.java文件：

执行JAVAC命令后，在同个文件目录下生成SpidHandle.class
将CMD窗口退回到包的根目录下，如spidHandle工程路径为：
Z:\project\work_workspace\spidhandle
其中通过编译后的SpidHandle.class存在于目录下：
Z:\project\work_workspace\spidhandle\src\com\spidHandle\api
由于SpidHandle类所在的包是com.spidHandle.api，所以CMD命令窗口要退回到Z:\project\work_workspace\spidhandle\src目录
然后在CMD窗口中执行

执行后在Z:\project\work_workspace\spidhandle\src目录下生成文件
com_spidHandle_api_SpidHandle.h文件。
安装VC6.0开发工具。如果你是在windows下开发,那可以先生成DLL,这样你就可以在Windows下调试。其实JNI调用DLL和SO是一样的，只是运行的操作系统不一样而已。下面是如何用VC6.0创建一个DLL项目。
创建一个项目工程，名为spidhandle的工程，创建过程如下：
1、打开VC6.0->文件->新建
2、在弹出窗口中的工程选项卡中选择Win32 Dynamic-Link Library;工程名命名为spidhandle;点击确定。
3、在新的提示窗口中选择一个空白的DLL工程，点击完成。
4、在菜单的工具栏中选择选项，弹出选项窗口。切换到目录选项卡
5、在目录选项卡中新建目录，新建的目录为你JDK所在的目录下的include目录，如：
   D:\Program Files\Java\jdk1.6.0_16\include
  再新建一个目录，新建的目录为include文件夹下的win32目录，如
   D:\Program Files\Java\jdk1.6.0_16\include\win32
  此步主要是向工程引入jni所需要的头文件，如include中包含了jni.h,jni_md.h
6、将com_spidHandle_api_SpidHandle.h头文件拷贝到vc6.0工程spidHandle根目录下，将其添加到工 程的Header Files，右键工程窗口中的Header Files,选择添加文件到目录下，选择工程路径下的com_spidHandle_api_SpidHandle.h文件。
7、在spidHandle工程根目录的文件夹中新建com_spidHandle_api_SpidHandle.h头文件对应的cpp文件， 文件名称为com_spidHandle_api_SpidHandle.cpp,然后返回VC6.0操作界面，将其添加到工程的Source Files,右键工程窗口中的Source Files,选择添加文件到目录下，选择工程路径下的com_spidHandle_api_SpidHandle.cpp文件。

8、将MD5.h,MD5.cpp拷贝到工程目录下，即跟com_spidHandle_api_SpidHandle.h文件同在项目根目录下。这两个文件其实是我用到的加密类。不是VC自有的，是另外同事开发的。
9、在VC6.0的菜单栏中选择组建；在工程文件夹下的Debug文件夹中生成spidHandle.dll
10、可以将spidHandle.dll拷贝到JAVA PROJECT的spidHandle的项目里，放在项目的根目录，即Z:\project\work_workspace\spidhandle目录 下，用eclispe运行SpidHandle.java文件。在输出窗口中会打印com_spidHandle_api_SpidHandle.cpp
的printf输出部分。

生成so文件，此步需要在linux上操作。
1、将com_spidHandle_api_SpidHandle.h, MD5.h,com_spidHandle_api_SpidHandle.cpp,MD5.cpp文件拷贝到linux下，如拷贝到/home/spidHandle目录中去；
2、在linux下，命令切换到spidHandle文件夹下，执行：
g++ com_spidHandle_api_SpidHandle.cpp MD5.cpp -I/usr/java/jdk1.6.0_16/include -I/usr/java/jdk1.6.0_16/include/linux -fPIC -shared -o libspidhandle.so
命令。其中-I/usr/java/jdk1.6.0_16/include
-I/usr/java/jdk1.6.0_16/include/linux 表示需要引入的头文件。相当于生成DLL引入了jni.h等文件。-fPIC表示生成共享库文件，libspidhandle.so表示库文件名。
3、执行export LD_LIBRARY_PATH=/home/spidHandle
  此步是设置将库文件所在路径加入LD_LIBRARY_PATH中去，如果不执行此步，在运行中就会出现异常：

4、可以在Linux中部署一个简单的web 应用，如一个简单的test项目，在servlet中调用该so，调用代码如下：

spid为加密后返回的结果。


补充：
过程中所碰到的问题：

问题1
java.lang.UnsatisfiedLinkError: /home/spidhandle/libspidhandle.so: /home/spidhandle/libspidhandle.so: wrong ELF class: ELFCLASS64 (Possible cause: architecture word width mismatch)

在linux中，用servlet调用该so,出现上面的异常，主要因为我所部署应用的linux服务器是64位的，而所生成的so是32位的，后来将项目部署到32位的服务器上就解决问题了。
如何查看linux操作系统是32位还是64位的，可以运行下面命令：
查看操作系统位数


问题2
运行servlet，JVM崩溃，并输出JVM异常，异常文件在tomcat启动文件startup.sh同个目录下，如tomcat/bin下，文件格式为hs_err_pid*.log 如，hs_err_pid23600.log
错误日志内容：
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0xb6e5a1ef, pid=23600, tid=2431036272
#
# JRE version: 6.0_16-b01
# Java VM: Java HotSpot(TM) Server VM (14.2-b01 mixed mode linux-x86 )
# Problematic frame:
# V  [libjvm.so+0x3931ef]
#
# If you would like to submit a bug report, please visit:
#   http://java.sun.com/webapps/bugreport/crash.jsp
#

---------------  T H R E A D  ---------------

Current thread (0x085bbc00):  JavaThread "http-8080-1" daemon [_thread_in_vm, id=23622, stack(0x90e1a000,0x90e6b000)]

siginfo:si_signo=SIGSEGV: si_errno=0, si_code=1 (SEGV_MAPERR), si_addr=0x00000000

Registers:
EAX=0x00000000, EBX=0xb71dd7c0, ECX=0xb71f87e0, EDX=0x00000ffc
ESP=0x90e696d4, EBP=0x90e69748, ESI=0x0825b0a8, EDI=0x00090e69
EIP=0xb6e5a1ef, CR2=0x00000000, EFLAGS=0x00010296

Top of Stack: (sp=0x90e696d4)
0x90e696d4:   b71d5ec8 00000000 b6e5a127 b7783a30
0x90e696e4:   b77624c0 00000000 90e69700 0825b0a8
0x90e696f4:   080de058 080de060 080de44c 085bbc00
0x90e69704:   00000000 b77d8ff4 9106c730 085bbc00
0x90e69714:   90e69750 b77c7f56 9106c8e8 085bbc00
0x90e69724:   00000001 00000005 00000000 90dd6601
0x90e69734:   90dd6000 00004044 90dd9ff4 927ec5f4
0x90e69744:   085bbc00 90e69768 90dd6fbd 085bbd10

Instructions: (pc=0xb6e5a1ef)
0xb6e5a1df:   ac 8b 46 08 89 45 b0 8b 46 0c 89 45 b4 8b 45 0c
0xb6e5a1ef:   8b 00 50 e8 09 ae fd ff 83 ec 0c 89 c7 50 e8 aa

Stack: [0x90e1a000,0x90e6b000],  sp=0x90e696d4,  free space=317k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0x3931ef]
C  [libspidhandle.so+0xfbd]  _ZN7JNIEnv_17GetStringUTFCharsEP8_jstringPh+0x27
C  [libspidhandle.so+0xc6e]  Java_com_spidHandle_api_SpidHandle_getSPID+0x52
j  com.spidHandle.api.SpidHandle.getSPID(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;+0
j  com.spidHandle.api.SpidHandle.buildSpID(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;+6
j  com.play.servlet.PlayServlet.service(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+1044
j  org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+376
j  org.apache.catalina.core.ApplicationFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+101
j  org.apache.catalina.core.StandardWrapperValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+804
j  org.apache.catalina.core.StandardContextValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+365
j  org.apache.catalina.core.StandardHostValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+64
j  org.apache.catalina.valves.ErrorReportValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+6
j  org.apache.catalina.core.StandardEngineValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+42
j  org.apache.catalina.connector.CoyoteAdapter.service(Lorg/apache/coyote/Request;Lorg/apache/coyote/Response;)V+158
j  org.apache.coyote.http11.Http11Processor.process(Ljava/net/Socket;)V+514
j  org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Ljava/net/Socket;)Z+82
j  org.apache.tomcat.util.net.JIoEndpoint$Worker.run()V+41
j  java.lang.Thread.run()V+11
v  ~StubRoutines::call_stub
V  [libjvm.so+0x36ca20]
V  [libjvm.so+0x530828]
V  [libjvm.so+0x36c227]
V  [libjvm.so+0x36c2da]
V  [libjvm.so+0x3e95f5]
V  [libjvm.so+0x61097e]
V  [libjvm.so+0x531cce]
C  [libpthread.so.0+0x6725]

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j  com.spidHandle.api.SpidHandle.getSPID(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;+0
j  com.spidHandle.api.SpidHandle.buildSpID(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;+6
j  com.play.servlet.PlayServlet.service(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+1044
j  org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+376
j  org.apache.catalina.core.ApplicationFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V+101
j  org.apache.catalina.core.StandardWrapperValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+804
j  org.apache.catalina.core.StandardContextValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+365
j  org.apache.catalina.core.StandardHostValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+64
j  org.apache.catalina.valves.ErrorReportValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+6
j  org.apache.catalina.core.StandardEngineValve.invoke(Lorg/apache/catalina/connector/Request;Lorg/apache/catalina/connector/Response;)V+42
j  org.apache.catalina.connector.CoyoteAdapter.service(Lorg/apache/coyote/Request;Lorg/apache/coyote/Response;)V+158
j  org.apache.coyote.http11.Http11Processor.process(Ljava/net/Socket;)V+514
j  org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Ljava/net/Socket;)Z+82
j  org.apache.tomcat.util.net.JIoEndpoint$Worker.run()V+41
j  java.lang.Thread.run()V+11
v  ~StubRoutines::call_stub

---------------  P R O C E S S  ---------------

Java Threads: ( => current thread )
=>0x085bbc00 JavaThread "http-8080-1" daemon [_thread_in_vm, id=23622, stack(0x90e1a000,0x90e6b000)]
  0x912ecc00 JavaThread "TP-Monitor" daemon [_thread_blocked, id=23619, stack(0x90e6b000,0x90ebc000)]
  0x91069c00 JavaThread "TP-Processor4" daemon [_thread_in_native, id=23618, stack(0x90ebc000,0x90f0d000)]
  0x9105f400 JavaThread "TP-Processor3" daemon [_thread_blocked, id=23617, stack(0x90f0d000,0x90f5e000)]
  0x9102f800 JavaThread "TP-Processor2" daemon [_thread_blocked, id=23616, stack(0x90f5e000,0x90faf000)]
  0x912ea400 JavaThread "TP-Processor1" daemon [_thread_blocked, id=23615, stack(0x90faf000,0x91000000)]
  0x912da000 JavaThread "http-8080-Acceptor-0" daemon [_thread_in_native, id=23614, stack(0x9113c000,0x9118d000)]
  0x91036000 JavaThread "ContainerBackgroundProcessor[StandardEngine[Catalina]]" daemon [_thread_blocked, id=23613, stack(0x9118d000,0x911de000)]
  0x912ac400 JavaThread "GC Daemon" daemon [_thread_blocked, id=23612, stack(0x91305000,0x91356000)]
  0x91615c00 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=23610, stack(0x9141d000,0x9146e000)]
  0x91613c00 JavaThread "CompilerThread1" daemon [_thread_blocked, id=23609, stack(0x9146e000,0x914ef000)]
  0x91612000 JavaThread "CompilerThread0" daemon [_thread_blocked, id=23608, stack(0x914ef000,0x91570000)]
  0x91610800 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=23607, stack(0x91570000,0x915c1000)]
  0x91600800 JavaThread "Finalizer" daemon [_thread_blocked, id=23606, stack(0x9170f000,0x91760000)]
  0x080d8400 JavaThread "Reference Handler" daemon [_thread_blocked, id=23605, stack(0x91760000,0x917b1000)]
  0x08058400 JavaThread "main" [_thread_in_native, id=23601, stack(0xb6a4e000,0xb6a9f000)]

Other Threads:
  0x080d4400 VMThread [stack: 0x917b1000,0x91832000] [id=23604]
  0x91617800 WatcherThread [stack: 0x9139c000,0x9141d000] [id=23611]

VM state:not at safepoint (normal execution)

VM Mutex/Monitor currently owned by a thread: None

Heap
PSYoungGen      total 24448K, used 339K [0xb0420000, 0xb1da0000, 0xb3900000)
  eden space 23168K, 1% used [0xb0420000,0xb0474cf8,0xb1ac0000)
  from space 1280K, 0% used [0xb1c20000,0xb1c20000,0xb1d60000)
  to   space 1408K, 0% used [0xb1ac0000,0xb1ac0000,0xb1c20000)
PSOldGen        total 27072K, used 8597K [0x95d00000, 0x97770000, 0xb0420000)
  object space 27072K, 31% used [0x95d00000,0x96565510,0x97770000)
PSPermGen       total 19200K, used 11186K [0x91d00000, 0x92fc0000, 0x95d00000)
  object space 19200K, 58% used [0x91d00000,0x927ec980,0x92fc0000)

Dynamic libraries:
08048000-08052000 r-xp 00000000 08:03 5775425    /usr/java/jdk1.6.0_16/bin/java
08052000-08053000 rwxp 00009000 08:03 5775425    /usr/java/jdk1.6.0_16/bin/java
08053000-08c64000 rwxp 00000000 00:00 0          [heap]
90cac000-90cb9000 r-xp 00000000 08:03 28295296   /lib/libgcc_s.so.1
90cb9000-90cba000 r-xp 0000c000 08:03 28295296   /lib/libgcc_s.so.1
90cba000-90cbb000 rwxp 0000d000 08:03 28295296   /lib/libgcc_s.so.1
90cbb000-90da3000 r-xp 00000000 08:03 5337022    /usr/lib/libstdc++.so.6.0.10
90da3000-90da7000 r-xp 000e7000 08:03 5337022    /usr/lib/libstdc++.so.6.0.10
90da7000-90da8000 rwxp 000eb000 08:03 5337022    /usr/lib/libstdc++.so.6.0.10
90da8000-90dae000 rwxp 00000000 00:00 0
90dd6000-90dd9000 r-xp 00000000 08:03 27729947   /home/play/lib/libspidhandle.so
90dd9000-90dda000 r-xp 00002000 08:03 27729947   /home/play/lib/libspidhandle.so
90dda000-90ddb000 rwxp 00003000 08:03 27729947   /home/play/lib/libspidhandle.so
90ddb000-90ddc000 r-xs 0000e000 08:03 5808917    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/spidhandle.jar
90ddc000-90ddd000 r-xs 00001000 08:03 5808916    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/slf4j-simple-1.5.8.jar
90ddd000-90ddf000 r-xs 00004000 08:03 5808915    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/slf4j-api-1.5.6.jar
90ddf000-90de5000 r-xs 00035000 08:03 5808914    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/logback-core-0.9.15.jar
90de5000-90dea000 r-xs 00023000 08:03 5808913    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/logback-classic-0.9.15.jar
90dea000-90df1000 r-xs 00059000 08:03 5808912    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/log4j-1.2.15.jar
90df1000-90dfd000 r-xs 000a2000 08:03 5808911    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/jxl.jar
90dfd000-90e07000 r-xs 0005c000 08:03 5808910    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/jstl-1.2.jar
90e07000-90e1a000 r-xs 00114000 08:03 5808909    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/jsf-impl.jar
90e1a000-90e1d000 ---p 00000000 00:00 0
90e1d000-90e6b000 rwxp 00000000 00:00 0          [threadstack:0004d494]
90e6b000-90e6e000 ---p 00000000 00:00 0
90e6e000-90ebc000 rwxp 00000000 00:00 0
90ebc000-90ebf000 ---p 00000000 00:00 0
90ebf000-90f0d000 rwxp 00000000 00:00 0
90f0d000-90f10000 ---p 00000000 00:00 0
90f10000-90f5e000 rwxp 00000000 00:00 0
90f5e000-90f61000 ---p 00000000 00:00 0
90f61000-90faf000 rwxp 00000000 00:00 0
90faf000-90fb2000 ---p 00000000 00:00 0
90fb2000-91000000 rwxp 00000000 00:00 0
91000000-910b3000 rwxp 00000000 00:00 0
910b3000-91100000 ---p 00000000 00:00 0
91100000-91105000 r-xs 0004a000 08:03 5808908    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/jsf-api.jar
91105000-91107000 r-xs 0000d000 08:03 5808907    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/commons-logging-1.1.1.jar
91107000-9113c000 r-xs 00000000 08:03 20439789   /var/run/nscd/dbl5FOXp (deleted)
9113c000-9113f000 ---p 00000000 00:00 0
9113f000-9118d000 rwxp 00000000 00:00 0
9118d000-91190000 ---p 00000000 00:00 0
91190000-911de000 rwxp 00000000 00:00 0
911de000-911f1000 r-xp 00000000 08:03 5784005    /usr/java/jdk1.6.0_16/jre/lib/i386/libnet.so
911f1000-911f2000 rwxp 00013000 08:03 5784005    /usr/java/jdk1.6.0_16/jre/lib/i386/libnet.so
911f2000-911f5000 r-xs 00027000 08:03 5783936    /usr/java/jdk1.6.0_16/jre/lib/ext/sunjce_provider.jar
911f5000-911fc000 r-xs 00091000 08:03 5784036    /usr/java/jdk1.6.0_16/jre/lib/jsse.jar
911fc000-91200000 r-xs 00035000 08:03 5783937    /usr/java/jdk1.6.0_16/jre/lib/ext/sunpkcs11.jar
91200000-912f8000 rwxp 00000000 00:00 0
912f8000-91300000 ---p 00000000 00:00 0
91300000-91302000 r-xs 0000a000 08:03 5808906    /usr/apache-tomcat-6.0.32/webapps/play/WEB-INF/lib/commons-codec-1.3.jar
91302000-91305000 r-xs 00013000 08:03 5784024    /usr/java/jdk1.6.0_16/jre/lib/jce.jar
91305000-91308000 ---p 00000000 00:00 0
91308000-91356000 rwxp 00000000 00:00 0
91356000-91359000 r-xs 000cb000 08:03 5783821    /usr/java/jdk1.6.0_16/jre/lib/ext/localedata.jar
91359000-9135d000 r-xs 00036000 08:03 5808320    /usr/apache-tomcat-6.0.32/lib/catalina-tribes.jar
9135d000-91360000 r-xs 0000f000 08:03 5808331    /usr/apache-tomcat-6.0.32/lib/tomcat-i18n-es.jar
91360000-9136a000 r-xs 000b1000 08:03 5808329    /usr/apache-tomcat-6.0.32/lib/tomcat-coyote.jar
9136a000-91371000 r-xs 0007a000 08:03 5808325    /usr/apache-tomcat-6.0.32/lib/jasper.jar
91371000-91380000 r-xs 0011a000 08:03 5808321    /usr/apache-tomcat-6.0.32/lib/catalina.jar
91380000-91382000 r-xs 0001e000 08:03 5808319    /usr/apache-tomcat-6.0.32/lib/catalina-ha.jar
91382000-91386000 r-xs 0003a000 08:03 5808330    /usr/apache-tomcat-6.0.32/lib/tomcat-dbcp.jar
91386000-91388000 r-xs 0000c000 08:03 5808318    /usr/apache-tomcat-6.0.32/lib/catalina-ant.jar
91388000-9138a000 r-xs 00007000 08:03 5808323    /usr/apache-tomcat-6.0.32/lib/el-api.jar
9138a000-9138c000 r-xs 00014000 08:03 5808328    /usr/apache-tomcat-6.0.32/lib/servlet-api.jar
9138c000-9139a000 r-xs 00170000 08:03 5808322    /usr/apache-tomcat-6.0.32/lib/ecj-3.3.1.jar
9139a000-9139c000 r-xs 0000c000 08:03 5808333    /usr/apache-tomcat-6.0.32/lib/tomcat-i18n-ja.jar
9139c000-9139d000 ---p 00000000 00:00 0
9139d000-9141d000 rwxp 00000000 00:00 0
9141d000-91420000 ---p 00000000 00:00 0
91420000-9146e000 rwxp 00000000 00:00 0
9146e000-91471000 ---p 00000000 00:00 0
91471000-914ef000 rwxp 00000000 00:00 0
914ef000-914f2000 ---p 00000000 00:00 0
914f2000-91570000 rwxp 00000000 00:00 0
91570000-91573000 ---p 00000000 00:00 0
91573000-915c1000 rwxp 00000000 00:00 0
915c1000-91600000 r-xp 00000000 08:03 5546089    /usr/lib/locale/en_US.utf8/LC_CTYPE
91600000-916ff000 rwxp 00000000 00:00 0
916ff000-91700000 ---p 00000000 00:00 0
91700000-91701000 rwxp 00000000 00:00 0
91701000-91703000 r-xs 00011000 08:03 5808326    /usr/apache-tomcat-6.0.32/lib/jsp-api.jar
91703000-91705000 r-xs 0000b000 08:03 5808332    /usr/apache-tomcat-6.0.32/lib/tomcat-i18n-fr.jar
91705000-91708000 r-xs 00019000 08:03 5808324    /usr/apache-tomcat-6.0.32/lib/jasper-el.jar
91708000-9170e000 r-xp 00000000 08:03 5784001    /usr/java/jdk1.6.0_16/jre/lib/i386/libmanagement.so
9170e000-9170f000 rwxp 00005000 08:03 5784001    /usr/java/jdk1.6.0_16/jre/lib/i386/libmanagement.so
9170f000-91712000 ---p 00000000 00:00 0
91712000-91760000 rwxp 00000000 00:00 0
91760000-91763000 ---p 00000000 00:00 0
91763000-917b1000 rwxp 00000000 00:00 0
917b1000-917b2000 ---p 00000000 00:00 0
917b2000-91865000 rwxp 00000000 00:00 0
91865000-919fb000 r-xs 02fb3000 08:03 5784038    /usr/java/jdk1.6.0_16/jre/lib/rt.jar
919fb000-919fc000 ---p 00000000 00:00 0
919fc000-91a7c000 rwxp 00000000 00:00 0
91a7c000-91a7d000 ---p 00000000 00:00 0
91a7d000-91b07000 rwxp 00000000 00:00 0
91b07000-91b1d000 rwxp 00000000 00:00 0
91b1d000-91b2b000 rwxp 00000000 00:00 0
91b2b000-91bf1000 rwxp 00000000 00:00 0
91bf1000-91bfb000 rwxp 00000000 00:00 0
91bfb000-91c11000 rwxp 00000000 00:00 0
91c11000-91c1f000 rwxp 00000000 00:00 0
91c1f000-91ce4000 rwxp 00000000 00:00 0
91ce4000-91cf2000 rwxp 00000000 00:00 0
91cf2000-91cff000 rwxp 00000000 00:00 0
91cff000-92fc0000 rwxp 00000000 00:00 0
92fc0000-95d00000 rwxp 00000000 00:00 0
95d00000-97770000 rwxp 00000000 00:00 0
97770000-b0420000 rwxp 00000000 00:00 0
b0420000-b1da0000 rwxp 00000000 00:00 0
b1da0000-b3900000 rwxp 00000000 00:00 0
b3900000-b3901000 r-xs 00003000 08:03 5808317    /usr/apache-tomcat-6.0.32/lib/annotations-api.jar
b3901000-b3902000 r-xs 00006000 08:03 5808298    /usr/apache-tomcat-6.0.32/bin/tomcat-juli.jar
b3902000-b3903000 r-xs 00005000 08:03 5808288    /usr/apache-tomcat-6.0.32/bin/commons-daemon.jar
b3903000-b390a000 r-xs 00000000 08:03 5523095    /usr/lib/gconv/gconv-modules.cache
b390a000-b3913000 rwxp 00000000 00:00 0
b3913000-b39ca000 rwxp 00000000 00:00 0
b39ca000-b3c0a000 rwxp 00000000 00:00 0
b3c0a000-b69ca000 rwxp 00000000 00:00 0
b69ca000-b69d9000 r-xp 00000000 08:03 5784014    /usr/java/jdk1.6.0_16/jre/lib/i386/libzip.so
b69d9000-b69db000 rwxp 0000e000 08:03 5784014    /usr/java/jdk1.6.0_16/jre/lib/i386/libzip.so
b69db000-b69e3000 rwxs 00000000 08:03 6743707    /tmp/hsperfdata_root/23600
b69e3000-b6a18000 r-xs 00000000 08:03 20439787   /var/run/nscd/passwd
b6a18000-b6a1e000 r-xp 00000000 08:03 5784018    /usr/java/jdk1.6.0_16/jre/lib/i386/native_threads/libhpi.so
b6a1e000-b6a1f000 rwxp 00006000 08:03 5784018    /usr/java/jdk1.6.0_16/jre/lib/i386/native_threads/libhpi.so
b6a1f000-b6a42000 r-xp 00000000 08:03 5783990    /usr/java/jdk1.6.0_16/jre/lib/i386/libjava.so
b6a42000-b6a44000 rwxp 00023000 08:03 5783990    /usr/java/jdk1.6.0_16/jre/lib/i386/libjava.so
b6a44000-b6a4c000 r-xp 00000000 08:03 28295217   /lib/librt-2.11.1.so
b6a4c000-b6a4d000 r-xp 00007000 08:03 28295217   /lib/librt-2.11.1.so
b6a4d000-b6a4e000 rwxp 00008000 08:03 28295217   /lib/librt-2.11.1.so
b6a4e000-b6a51000 ---p 00000000 00:00 0
b6a51000-b6a9f000 rwxp 00000000 00:00 0
b6a9f000-b6ac5000 r-xp 00000000 08:03 28295195   /lib/libm-2.11.1.so
b6ac5000-b6ac6000 r-xp 00026000 08:03 28295195   /lib/libm-2.11.1.so
b6ac6000-b6ac7000 rwxp 00027000 08:03 28295195   /lib/libm-2.11.1.so
b6ac7000-b7194000 r-xp 00000000 08:03 5784022    /usr/java/jdk1.6.0_16/jre/lib/i386/server/libjvm.so
b7194000-b71e2000 rwxp 006cc000 08:03 5784022    /usr/java/jdk1.6.0_16/jre/lib/i386/server/libjvm.so
b71e2000-b7605000 rwxp 00000000 00:00 0
b7605000-b7760000 r-xp 00000000 08:03 28295187   /lib/libc-2.11.1.so
b7760000-b7762000 r-xp 0015b000 08:03 28295187   /lib/libc-2.11.1.so
b7762000-b7763000 rwxp 0015d000 08:03 28295187   /lib/libc-2.11.1.so
b7763000-b7767000 rwxp 00000000 00:00 0
b7767000-b776a000 r-xp 00000000 08:03 28295193   /lib/libdl-2.11.1.so
b776a000-b776b000 r-xp 00002000 08:03 28295193   /lib/libdl-2.11.1.so
b776b000-b776c000 rwxp 00003000 08:03 28295193   /lib/libdl-2.11.1.so
b776c000-b7773000 r-xp 00000000 08:03 5783973    /usr/java/jdk1.6.0_16/jre/lib/i386/jli/libjli.so
b7773000-b7775000 rwxp 00006000 08:03 5783973    /usr/java/jdk1.6.0_16/jre/lib/i386/jli/libjli.so
b7775000-b778c000 r-xp 00000000 08:03 28295213   /lib/libpthread-2.11.1.so
b778c000-b778d000 r-xp 00016000 08:03 28295213   /lib/libpthread-2.11.1.so
b778d000-b778e000 rwxp 00017000 08:03 28295213   /lib/libpthread-2.11.1.so
b778e000-b7790000 rwxp 00000000 00:00 0
b7790000-b7791000 r-xs 00005000 08:03 5808283    /usr/apache-tomcat-6.0.32/bin/bootstrap.jar
b7791000-b7792000 rwxp 00000000 00:00 0
b7792000-b7793000 r-xp 00000000 00:00 0
b7793000-b77a8000 r-xp 00000000 08:03 28295198   /lib/libnsl-2.11.1.so
b77a8000-b77a9000 r-xp 00014000 08:03 28295198   /lib/libnsl-2.11.1.so
b77a9000-b77aa000 rwxp 00015000 08:03 28295198   /lib/libnsl-2.11.1.so
b77aa000-b77ac000 rwxp 00000000 00:00 0
b77ac000-b77b7000 r-xp 00000000 08:03 5784013    /usr/java/jdk1.6.0_16/jre/lib/i386/libverify.so
b77b7000-b77b8000 rwxp 0000b000 08:03 5784013    /usr/java/jdk1.6.0_16/jre/lib/i386/libverify.so
b77b8000-b77b9000 rwxp 00000000 00:00 0
b77b9000-b77d8000 r-xp 00000000 08:03 28295180   /lib/ld-2.11.1.so
b77d8000-b77d9000 r-xp 0001e000 08:03 28295180   /lib/ld-2.11.1.so
b77d9000-b77da000 rwxp 0001f000 08:03 28295180   /lib/ld-2.11.1.so
bfcc6000-bfcdb000 rwxp 00000000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

VM Arguments:
jvm_args: -Djava.util.logging.config.file=/usr/apache-tomcat-6.0.32/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/apache-tomcat-6.0.32/endorsed -Dcatalina.base=/usr/apache-tomcat-6.0.32 -Dcatalina.home=/usr/apache-tomcat-6.0.32 -Djava.io.tmpdir=/usr/apache-tomcat-6.0.32/temp
java_command: org.apache.catalina.startup.Bootstrap start
Launcher Type: SUN_STANDARD

Environment Variables:
JAVA_HOME=/usr/java/jdk1.6.0_16
CLASSPATH=/usr/apache-tomcat-6.0.32/bin/bootstrap.jar
PATH=/sbin:/usr/sbin:/usr/local/sbin:/root/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/X11R6/bin:/usr/games:/usr/lib/mit/bin:/usr/lib/mit/sbin:/usr/java/jdk1.6.0_16/bin:/usr/java/jdk1.6.0_16/jre/bin
LD_LIBRARY_PATH=/usr/java/jdk1.6.0_16/jre/lib/i386/server:/usr/java/jdk1.6.0_16/jre/lib/i386:/usr/java/jdk1.6.0_16/jre/../lib/i386:/home/play/lib
SHELL=/bin/bash
HOSTTYPE=i386
OSTYPE=linux
MACHTYPE=i686-suse-linux

Signal Handlers:
SIGSEGV: [libjvm.so+0x650710], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGBUS: [libjvm.so+0x650710], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGFPE: [libjvm.so+0x52f600], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGPIPE: [libjvm.so+0x52f600], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGXFSZ: [libjvm.so+0x52f600], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGILL: [libjvm.so+0x52f600], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGUSR1: SIG_DFL, sa_mask[0]=0x00000000, sa_flags=0x00000000
SIGUSR2: [libjvm.so+0x5321f0], sa_mask[0]=0x00000000, sa_flags=0x10000004
SIGHUP: [libjvm.so+0x531f20], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGINT: SIG_IGN, sa_mask[0]=0x00000000, sa_flags=0x00000000
SIGTERM: [libjvm.so+0x531f20], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004
SIGQUIT: [libjvm.so+0x531f20], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004


---------------  S Y S T E M  ---------------

OS:SUSE Linux Enterprise Server 11 (i586)
VERSION = 11
PATCHLEVEL = 1

uname:Linux 2.6.32.12-0.7-pae #1 SMP 2010-05-20 11:14:20 +0200 i686
libc:glibc 2.11.1 NPTL 2.11.1
rlimit: STACK 8192k, CORE 1k, NPROC 15118, NOFILE 8192, AS 3192000k
load average:0.00 0.04 0.05

CPU:total 2 (2 cores per cpu, 1 threads per core) family 6 model 23 stepping 10, cmov, cx8, fxsr, mmx, sse, sse2, sse3, ssse3

Memory: 4k page, physical 1941704k(213752k free), swap 2048276k(1540564k free)

vm_info: Java HotSpot(TM) Server VM (14.2-b01) for linux-x86 JRE (1.6.0_16-b01), built on Jul 31 2009 06:03:51 by "java_re" with gcc 3.2.1-7a (J2SE release)

time: Sat Mar 12 17:13:08 2011
elapsed time: 27 seconds

一开始以为是JVM无法释放C的对象，但后来发现


并没有出现堆栈缢出的现象，所以排除该原因。

查阅 文档:
      JavaTM 2 Platform, Standard Edition 5.0
      Troubleshooting and Diagnostic Guide
      文档中提到:
     
      If you get a crash in a native application library (like the above examples) then you may be able to
      attach the native debugger (dbx, gdb, windbg depending on the operating system) to the core file/crash
      dump if it is available. Another approach is run with the -Xcheck:jni option added to the command
      line (section 1.17.3). The -Xcheck:jni option is not guaranteed to find all issues with JNI code but it
      can help identify a significant number of issues.
     
      解决方法:
      启动JVM时增加启动参数 -Xcheck:jni
      日志中输出JNI的错误日志:
      JVM崩溃的原因找到了.是由于传入C方法体中某个参数值为NULL，如buildSpID(String path, String login_name, String password, String key)中login_name为NULL,导致传递给C程序的参数为NULL.NULL值传递给C,C不能识别他为字符串,所以JVM崩溃.

C:\Program Files\Java\jdk1.5.0_16
Exception in thread "main" java.lang.SecurityException: class "xx.xx"'s signer information does not match signer information of other classes in the same package
        at java.lang.ClassLoader.checkCerts(ClassLoader.java:775)
        at java.lang.ClassLoader.preDefineClass(ClassLoader.java:487)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:614)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
4)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
        at xx.xx(xx.java:80)

                

            @NotThreadSafe 

            public class NumberRange {

            private int lower, upper;

            

            public int getLower() { return lower; }

            public int getUpper() { return upper; }

            

            public void setLower(int value) { 

            if (value > upper) 

            throw new IllegalArgumentException(...);

            lower = value;

            }

            

            public void setUpper(int value) { 

            if (value < lower) 

            throw new IllegalArgumentException(...);

            upper = value;

            }

            }

            

                

            volatile boolean shutdownRequested;

            

            ...

            

            public void shutdown() { shutdownRequested = true; }

            

            public void doWork() { 

            while (!shutdownRequested) { 

            // do stuff

            }

            }

            

                

            public class BackgroundFloobleLoader {

            public volatile Flooble theFlooble;

            

            public void initInBackground() {

            // do lots of stuff

            theFlooble = new Flooble();  // this is the only write to theFlooble

            }

            }

            

            public class SomeOtherClass {

            public void doWork() {

            while (true) { 

            // do some stuff...

            // use the Flooble, but only if it is ready

            if (floobleLoader.theFlooble != null) 

            doSomething(floobleLoader.theFlooble);

            }

            }

            }

            

                

            public class UserManager {

            public volatile String lastUser;

            

            public boolean authenticate(String user, String password) {

            boolean valid = passwordIsValid(user, password);

            if (valid) {

            User u = new User();

            activeUsers.add(u);

            lastUser = user;

            }

            return valid;

            }

            } 

            

                

            @ThreadSafe

            public class Person {

            private volatile String firstName;

            private volatile String lastName;

            private volatile int age;

            

            public String getFirstName() { return firstName; }

            public String getLastName() { return lastName; }

            public int getAge() { return age; }

            

            public void setFirstName(String firstName) { 

            this.firstName = firstName;

            }

            

            public void setLastName(String lastName) { 

            this.lastName = lastName;

            }

            

            public void setAge(int age) { 

            this.age = age;

            }

            }

            

                

            @ThreadSafe

            public class CheesyCounter {

            // Employs the cheap read-write lock trick

            // All mutative operations MUST be done with the 'this' lock held

            @GuardedBy("this") private volatile int value;

            

            public int getValue() { return value; }

            

            public synchronized int increment() {

            return value++;

            }

            }

            

db2获得刚插入的自增字段的值：
values(identity_val_local())


Select Top在不同数据库中的使用用法：


1. Oracle数据库

<CENTER><CCID_NOBR> SELECT * FROM TABLE1 WHERE ROWNUM<=N



2. Infomix数据库


SELECT FIRST N * FROM TABLE1


3. DB2数据库


SELECT * ROW_NUMBER() OVER(ORDER BY COL1 DESC) AS ROWNUM WHERE ROWNUM<=N


或者


SELECT COLUMN FROM TABLE FETCH FIRST N ROWS ONLY



4. SQL Server数据库


SELECT TOP N * FROM TABLE1


5. Sybase数据库


SET ROWCOUNT N
GO
SELECT * FROM TABLE1



6. MySQL数据库


SELECT * FROM TABLE1 LIMIT N



7. FoxPro数据库


SELECT * TOP N FROM TABLE ORDER BY COLUMN

转载自http://tech.techweb.com.cn/archiver/tid-243262.html

新一篇: Sql确定两个日期之间的秒、分、小时数 | 旧一篇: Sql确定两个日期之间的秒、分、小时数

问题

求两个日期之间相差的月数或年数。例如，求第一个员工和最后一个员工聘用之间相差的月份数，以及这些月折合的年数。

解决方案

由于一年有12个月，因此，获得两个日期之间的月份数之后，再除以12，就能得到年数。在有了相应的解决方案 后，可以根据此年数的不同用途对结果进行舍/入。例如，表EMP中的第一个HIREDATE（聘用日期）是“17-DEC-1980”，最后一个 HIREDATE是“12-JAN-1983”。如果对年进行减法运算（1983减去1980），结果是3年。然而，月份差大约为25（两年多一点儿）。 所以应该修改解决方案。下列的解决方案返回的结果是25个月及2年。

DB2和MySQL

使用函数YEAR和MONTH为给定日期返回4位数的年份和两位数的月份：

1  select mnth, mnth/12

2    from (

3  select (year(max_hd) - year(min_hd))*12 +

4         (month(max_hd) - month(min_hd)) as mnth

5    from (

6  select min(hiredate) as min_hd, max(hiredate) as max_hd

7    from emp

8         ) x

9         ) y

Oracle

使用函数MONTHS_BETWEEN，将得到两个日期之间相差的月数（要得到相差年数，只需除以12即可）：

1  select months_between(max_hd,min_hd),

2         months_between(max_hd,min_hd)/12

3    from (

4  select min(hiredate) min_hd, max(hiredate) max_hd

5    from emp

6         ) x

PostgreSQL

使用函数EXTRACT，为给定日期返回4位数的年和两位数的月：

 1  select mnth, mnth/12

 2    from (

 3  select ( extract(year from max_hd) -

 4           extract(year from min_hd) ) * 12

 5         +

 6         ( extract(month from max_hd) -

 7           extract(month from min_hd) ) as mnth

 8    from (

 9  select min(hiredate) as min_hd, max(hiredate) as max_hd

10    from emp

11         ) x

12         ) y

SQL Server

使用函数DATEDIFF，得到两个日期之间相差的月数（要得到相差年数，只需除以12）：

1  select datediff(month,min_hd,max_hd),

2         datediff(month,min_hd,max_hd)/12

3    from (

4  select min(hiredate) min_hd, max(hiredate) max_hd

5    from emp

6         ) x

讨论

DB2、MySQL和PostgreSQL

除PostgreSQL解决方案中从MIN_HD和MAX_HD提取了年份、月份的方法不同外，对于这3个 RDBM，计算MIN_HD和MAX_HD之间相差年数和月数的方法都相同。下面的讨论适用于这3种数据库的解决方案。内联视图X返回表EMP中第一个 HIREDATE和最后一个HIREDATE，如下所示：

select min(hiredate) as min_hd,

       max(hiredate) as max_hd

  from emp

MIN_HD      MAX_HD

----------- -----------

17-DEC-1980 12-JAN-1983

要计算MIN_HD和MAX_HD 之间的月数，只需用年数差乘以12，然后再加上MIN_HD和MAX_HD之间的月数之差。如果不知道其中的机理，可以将这两个日期的有关部分显示出来。它们对年和月部分的数值如下所示：

select year(max_hd)  as max_yr,   year(min_hd) as min_yr,

       month(max_hd) as max_mon, month(min_hd) as min_mon

  from (

select min(hiredate) as min_hd, max(hiredate) as max_hd

  from emp

       ) x

MAX_YR     MIN_YR    MAX_MON    MIN_MON

------ ---------- ---------- ----------

  1983       1980          1         12

观察上面的结果，会发现MIN_HD和MAX_HD之间相差的月数是(1983-1980)*12 + （1-12）。要得到MIN_HD和MAX_HD之间相差的年数，只需除以12即可，当然，还要根据用途，对相差年数进行相应的舍/入操作。

Oracle和SQL Server

内联视图X返回表EMP中第一个HIREDATE和最后一个HIREDATE，如下所示：

select min(hiredate) as min_hd, max(hiredate) as max_hd

  from emp

MIN_HD      MAX_HD

----------- -----------

17-DEC-1980 12-JAN-1983

由Oracle和SQL Server提供的函数（分别为MONTHS_BETWEEN和DATEDIFF）可以返回两个给定日期之间的月份数。要得到年数，只需除以12即可。