请教关于下面这段代码

Question

queryDataSet1.close();
queryDataSet1.setQuery(new com.borland.dx.sql.dataset.QueryDescriptor(database1, sqlstatement, null, true, Load.ALL));
queryDataSet1.open();//你忘了打开DataSet

Answer 1

可加了这句还是不对阿
错误为
See com.borland.dx.dataset.DataSetException error code:  BASE+62com.borland.dx.dataset.DataSetException: Execution of query failed. at com.borland.dx.dataset.DataSetException.a(Unknown Source) at com.borland.dx.dataset.DataSetException.queryFailed(Unknown Source) at com.borland.dx.sql.dataset.QueryProvider.a(Unknown Source) at com.borland.dx.sql.dataset.JdbcProvider.provideData(Unknown Source) at com.borland.dx.dataset.StorageDataSet.a(Unknown Source) at com.borland.dx.dataset.DataSet.a(Unknown Source) at com.borland.dx.dataset.DataSet.open(Unknown Source) at com.seu.bank.admin.Main.jButton1_actionPerformed(Main.java:1151) at com.seu.bank.admin.Main$3.actionPerformed(Main.java:325) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1764) at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1817) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:419) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:257) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245) at java.awt.Component.processMouseEvent(Component.java:5093) at java.awt.Component.processEvent(Component.java:4890) at java.awt.Container.processEvent(Container.java:1566) at java.awt.Component.dispatchEventImpl(Component.java:3598) at java.awt.Container.dispatchEventImpl(Container.java:1623) at java.awt.Component.dispatchEvent(Component.java:3439) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3165) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095) at java.awt.Container.dispatchEventImpl(Container.java:1609) at java.awt.Window.dispatchEventImpl(Window.java:1585) at java.awt.Component.dispatchEvent(Component.java:3439) at java.awt.EventQueue.dispatchEvent(EventQueue.java:450) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136) at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)Chained exception:java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC]No ResultSet set was produced. at com.microsoft.jdbc.base.BaseExceptions.createException(Unknown Source) at com.microsoft.jdbc.base.BaseExceptions.getException(Unknown Source) at com.microsoft.jdbc.base.BaseStatement.executeQueryInternal(Unknown Source) at com.microsoft.jdbc.base.BasePreparedStatement.executeQuery(Unknown Source) at com.borland.dx.sql.dataset.o.f(Unknown Source) at com.borland.dx.sql.dataset.QueryProvider.e(Unknown Source) at com.borland.dx.sql.dataset.JdbcProvider.provideData(Unknown Source) at com.borland.dx.dataset.StorageDataSet.a(Unknown Source) at com.borland.dx.dataset.DataSet.a(Unknown Source) at com.borland.dx.dataset.DataSet.open(Unknown Source) at com.seu.bank.admin.Main.jButton1_actionPerformed(Main.java:1151) at com.seu.bank.admin.Main$3.actionPerformed(Main.java:325) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1764) at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1817) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:419) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:257) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245) at java.awt.Component.processMouseEvent(Component.java:5093) at java.awt.Component.processEvent(Component.java:4890) at java.awt.Container.processEvent(Container.java:1566) at java.awt.Component.dispatchEventImpl(Component.java:3598) at java.awt.Container.dispatchEventImpl(Container.java:1623) at java.awt.Component.dispatchEvent(Component.java:3439) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3165) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095) at java.awt.Container.dispatchEventImpl(Container.java:1609) at java.awt.Window.dispatchEventImpl(Window.java:1585) at java.awt.Component.dispatchEvent(Component.java:3439) at java.awt.EventQueue.dispatchEvent(EventQueue.java:450) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136) at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

Answer 2

还有一个问题就是
我要从数据库中返回一个查询结果，并将其储存为一个String值
用queryDataSet组件，这个代码该如何写?是这样吗？
queryDataSet1.close(); queryDataSet1.setQuery(new   com.borland.dx.sql.dataset.QueryDescriptor(database1, sqlstatement, null, true, Load.ALL));String sqlres = queryDataSet1.getString(0);queryDataSet1.open();
还是该如何写？

Answer 3

在SQL中，字符应该用单引号''括起来：
"SELECT U_Password FROM Userinfo WHERE UID = '" + Uname + "'"先open，再getString：
queryDataSet1.open();
String sqlres = queryDataSet1.getString(1);//index从1开始

Answer 4

queryDataSet1.empty();有什么作用？
在使用queryDataSet时，用不用把以前别的函数中在调用queryDataSet1.setQuery()时写的sql语句清空，还是queryDataSet1.close();就能达到这样的效果？
好像我记得在C++Builder中用ADOQuery进行sql语句查询时要清空，好像就这样：
ADOQuery1->Active = false;
ADOQuery1->SQL->Clear();
.....
ADOQuery1->Active = true;
在JBuilder中的queryDataSet要不要这样做呢？

Answer 5

String sqlres = queryDataSet1.getString(1);
sqlres将返回一个数字值，但是以String存储
String amount = jTextField1.getText();
amount为输入的一个数字值，如何对sqlres和amount的数字值的大小做比较？

Answer 6

不需要啊！只要关闭就可以了！Cbuilder也是可以不需要的！你只要使用 
SQL->SetText(_T(SQL))就行了！