使用java组合框只想从MS Access中删除选定的项目记录不是整个记录

Question

我正在使用java applet GUI应用程序，并希望这样做，当我按下删除按钮时，只有在组合框中选择的项目被删除从MS Access，但我下面的代码删除，全程记录从MS Access ..

code i tried is: 

if(e.getSource()==btn_del) 
    { 
     try 
       { 


        Connection con; 

        DriverManager.registerDriver(new sun.jdbc.odbc.JdbcOdbcDriver()); 

        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 

        con = DriverManager.getConnection("jdbc:odbc:dsnproj","",""); 

        Statement s=con.createStatement(); 

        String q="select * from trans_dest 
           where          
           dest='"+cmb_dest.getSelectedItem()+"'"; 

        ResultSet r=s.executeQuery(q); 

        while (r.next()) { 


         r1=r.getString(2); 

         System.out.println(r1); 

         r2=r.getString(3); 

         System.out.println(r2); 

         r3=r.getString(4); 
         System.out.println(r3); 

         r4=r.getString(5); 
         System.out.println(r4); 

         String qryd1,qryd2,qryd3,qryd4; 

         qryd1="DELETE route1 from trans_dest where route1='"+r1+"'"; 
         qryd2="DELETE route2 from trans_dest where route2='"+r2+"'"; 
         qryd3="DELETE route3 from trans_dest where route3='"+r3+"'"; 
         qryd4="DELETE route4 from trans_dest where route4='"+r4+"'"; 

         if(r1.equals(cmb_route.getSelectedItem())) 

         { 

          System.out.println("in 1st"); 
          int executeUpdate= s.executeUpdate(qryd1); 
          System.out.println(executeUpdate); 

         } 

         else if(r2.equals(cmb_route.getSelectedItem())) 

         { 

          System.out.println("in 2nd"); 

          int executeUpdate1 = s.executeUpdate(qryd2); 
          System.out.println(executeUpdate1); 
         } 

         else if(r3.equals(cmb_route.getSelectedItem())) 

         { 

          System.out.println("in 3rd"); 

          int executeUpdate2 = s.executeUpdate(qryd3); 
          System.out.println(executeUpdate2); 
         } 

         else if(r4.equals(cmb_route.getSelectedItem())) 

         { 

          System.out.println("in 4th"); 

          int executeUpdate3 = s.executeUpdate(qryd4); 
          System.out.println(executeUpdate3); 
         } 


       } 




       Frame f=new Frame(); 

       JOptionPane.showMessageDialog(f, "Deleted product Successfully... "); 

       System.out.println("deleted..."); 
     } 

}

没有错误，但只在我所选字段删除从我的数据库全程记录insted的的...

产量：

apple 
banana 
grapes 
null 
in 2nd 
1 
ResultSet is closed 

Answer 1

from my database insted of only on field which i selected.. 

这意味着你期待只删除选中的行。

按照DELETE查询查询，这是不可能的。 DELETE查询将查询满足where条件的表中的所有记录。

qryd2="DELETE route2 from trans_dest where route2='"+r2+"'"; 

这将从条件满足的条件删除数据库的整行。

编辑：

如果你想删除列值，您可以设置列值使用update query为null。

即UPDATE trans_dest SET route2= NULL where route2='"+r2+"'"

Answer 2

见这个例子也许这将是有益的。

import java.awt.BorderLayout; 
import javax.swing.*; 
import java.awt.event.*; 
import java.sql.*; 

public class ComboboxTest extends JFrame implements ActionListener{ 
    JComboBox combo ; 
    JButton del; 
    public ComboboxTest(){ 
     combo = new JComboBox(new String[]{"Apple","Orange","Banana"}); 
     del = new JButton("DELETE"); 
     del.addActionListener(this); 
     this.add(combo, BorderLayout.NORTH); 
     this.add(del,BorderLayout.SOUTH); 
     this.setSize(300,200); 
     this.setVisible(true); 
     this.setDefaultCloseOperation(3); 
    } 

    @Override 
    public void actionPerformed(ActionEvent e) { 
     JButton b = (JButton)e.getSource(); 
     if(b == del) { 
     String query = "update trans_dest set CellName='' where dest = " 
      + "'"+combo.getSelectedItem().toString()+"'"; 
     try{ 

       Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance(); 
       Connection c = DriverManager.getConnection("jdbc:odbc:dsnproj","",""); 
       Statement s = c.createStatement(); 
       s.executeUpdate(query); 
       System.out.println("Selected Item Removed ."); 
       s.close(); 

     }catch(Exception ex){ 
      System.out.println(ex.getMessage()); 
     } 
     }//end if 

    } 


    public static void main(String...args){ 
     new ComboboxTest(); 
    } 
}