PostgreSQL提供了一种叫做规则（Rule）的机制，来实现一些与触发器不同的更加自定义的功能。规则系统介于查询编译器和执行优化器之间，根据规则及修改查询。
基本语法：
CREATE RULE 规则名 AS
ON {SELECT | INSERT | UPDATE | DELETE}
TO 表名 [WHERE 规则条件]
DO [INSTEAD] {NOTHING | 命令 | (命令, 命令...)}
PostgreSQL中的视图实际上就是通过RULE来实现的。
例如建立一个视图:
CREATE VIEW view_1 AS SELECT * FROM table_1;
PostgreSQL实际将这个语句翻译为规则：
CREATE TABLE table_view_1 (涉及的列名);
CREATE RULE return AS
ON SELECT TO table_view_1 DO INSTEAD
SELECT * FROM table_1;
这样在查询view_1视图时，PostgreSQL实际上把它转换为对隐含的表table_view_1的查询。
在仅仅需要查询的时候，CREATE VIEW是更合适的语法，但是这这样建立的视图是不能做修改操作的，但是通过规则是可以做到的。
例如我们要更新view_1视图：
CREATE TABLE table_view_1 (涉及的列名);
CREATE RULE update_view_1 AS
ON UPDATE TO table_view_1
DO UPDATE table_1 SET col_1 = new.col_1
WHERE col_2 = new.col_2;
有了这样的规则，我们执行UPDATE view_1 SET col_1=x WHERE col_2=y;的时候，实际上就更新了table_1，这样就实现了更新视图。对于多表的视图，也可以这样操作。
为了轻量，我的Gentoo Linux用的Xfce桌面系统，一切都还不错，今天装ZendStudio遇到了些问题，记下。
安装的时候都很正常，解压下载的压缩包得到.bin文件，然后安装，也没有错，但是一启动就挂了。
查看了/home/plx/Zend/workspace/DefaultWorkspace7/.metadata/.log 发现如下异常：
!MESSAGE Application error
!STACK 1
org.eclipse.swt.SWTError: XPCOM error -2147467262
at org.eclipse.swt.browser.Mozilla.error(Mozilla.java:1688)
at org.eclipse.swt.browser.Mozilla.setText(Mozilla.java:1911)
at org.eclipse.swt.browser.Browser.setText(Browser.java:750)
at org.eclipse.ui.internal.intro.impl.presentations.BrowserIntroPartImplementation.generateContentForPage(BrowserIntroPartImplementation.java:363)
at org.eclipse.ui.internal.intro.impl.presentations.BrowserIntroPartImplementation.dynamicStandbyStateChanged(BrowserIntroPartImplementation.java:577)
at org.eclipse.ui.internal.intro.impl.presentations.BrowserIntroPartImplementation.doStandbyStateChanged(BrowserIntroPartImplementation.java:784)
at org.eclipse.ui.internal.intro.impl.model.AbstractIntroPartImplementation.standbyStateChanged(AbstractIntroPartImplementation.java:249)
at org.eclipse.ui.internal.intro.impl.model.IntroPartPresentation.standbyStateChanged(IntroPartPresentation.java:443)
at org.eclipse.ui.intro.config.CustomizableIntroPart.standbyStateChanged(CustomizableIntroPart.java:266)
at org.eclipse.ui.internal.ViewIntroAdapterPart$2.run(ViewIntroAdapterPart.java:74)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.ViewIntroAdapterPart.setStandby(ViewIntroAdapterPart.java:70)
at org.eclipse.ui.internal.ViewIntroAdapterPart$1.propertyChanged(ViewIntroAdapterPart.java:55)
at org.eclipse.ui.internal.WorkbenchPartReference.fireInternalPropertyChange(WorkbenchPartReference.java:375)
at org.eclipse.ui.internal.WorkbenchPartReference.fireZoomChange(WorkbenchPartReference.java:540)
at org.eclipse.ui.internal.PartPane.setZoomed(PartPane.java:356)
at org.eclipse.ui.internal.PartStack.setZoomed(PartStack.java:1526)
at org.eclipse.ui.internal.PartSashContainer.zoomIn(PartSashContainer.java:884)
at org.eclipse.ui.internal.PartSashContainer.childRequestZoomIn(PartSashContainer.java:905)
at org.eclipse.ui.internal.LayoutPart.requestZoomIn(LayoutPart.java:354)
at org.eclipse.ui.internal.PartStack.setState(PartStack.java:1501)
at org.eclipse.ui.internal.WorkbenchPage.setState(WorkbenchPage.java:3872)
at org.eclipse.ui.internal.WorkbenchPage.toggleZoom(WorkbenchPage.java:3944)
at org.eclipse.ui.internal.WorkbenchIntroManager.setIntroStandby(WorkbenchIntroManager.java:201)
at org.eclipse.ui.internal.WorkbenchIntroManager.showIntro(WorkbenchIntroManager.java:136)
at org.eclipse.ui.application.WorkbenchWindowAdvisor.openIntro(WorkbenchWindowAdvisor.java:173)
at org.eclipse.ui.internal.ide.application.IDEWorkbenchWindowAdvisor.openIntro(IDEWorkbenchWindowAdvisor.java:458)
at org.eclipse.ui.internal.WorkbenchWindow.open(WorkbenchWindow.java:777)
at org.eclipse.ui.internal.Workbench$22.runWithException(Workbench.java:1041)
at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:133)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3378)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3036)
at org.eclipse.ui.application.WorkbenchAdvisor.openWindows(WorkbenchAdvisor.java:803)
at org.eclipse.ui.internal.Workbench$27.runWithException(Workbench.java:1361)
at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:133)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3378)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3036)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2293)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2198)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:493)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:488)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:193)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:370)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:549)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
at org.eclipse.equinox.launcher.Main.run(Main.java:1236)
at org.eclipse.equinox.launcher.Main.main(Main.java:1212)
我以为是我没装JRE，但是安装目录下有JRE，Zend应该是调用自带的。
Google之，有人说删除xulrunner，我这依赖xulrunner的软件太多，不可能删。
发现有人说是少了个参数，
-Dorg.eclipse.swt.browser.XULRunnerPath=
这个java系统参数应该指定一个目录，但是这里可以任意写或者空着。
在添加该行后，重新启动ZendStudio，然后就可以把该行删除，以后再启动都不会报错了。
同理，因为ZendStudio基于Eclipse，所以Eclipse也适用。
