数据库连接问题

Question

import java.io.*;
import java.awt.event.*;
import java.awt.*;import javax.swing.*;
import java.sql.*;public class hhhh extends Frame
  {
     public static void main(String args[])
{
      
      Connection con;
        Statement sql=null;
        ResultSet rs;
TextField xuehao,xingming,banji,nianling,dianhua;
Panel p1,p2,p3,p4,p5;
  xuehao=new TextField(10);
         xingming=new TextField(10);
        banji=new TextField(10);
        nianling=new TextField(10);
        dianhua=new TextField(10);
       Frame fr=new Frame();
fr.setLayout(new GridLayout(3,1));
        p1=new Panel();
        p2=new Panel();
        p3=new Panel();
        p4=new Panel();
        p5=new Panel();
p1.add(new Label("xuehao"));p1.add(xuehao);
p2.add(new Label("xingming"));p2.add(xingming);  
p2.add(new Label("banji"));p3.add(banji);
p4.add(new Label("nianling"));p4.add(nianling);
p5.add(new Label("dianhua"));p5.add(dianhua); 
 fr.add(p1);fr.add(p2);fr.add(p3);fr.add(p4);
  fr.add(p5);
  System.out.println("OK Change");
  //addWindowListener(new WindowAdapter()
//{
  //public void windowClosing(WindowEvent e)
  //{
//System.exit(0);
  //}
//});
//repaint();  try
    {
       
             String Sxuehao,Sxingming,Sbanji,Snianling,Sdianhua;
             
             Sxuehao="'"+xuehao.getText().trim()+"'";
             Sxingming="'"+xingming.getText().trim()+"'";
             Sbanji="'"+banji.getText().trim()+"'";
             Snianling="'"+nianling.getText(). trim()+"'";
             Sdianhua="'"+dianhua.getText(). trim()+"'";
           String temp="UPDATE lai SET xuehao="+Sxuehao+"xingming="+Sxingming+"banji="+Sbanji+"nianling="+Snianling+" WHRER dianhua="+Sdianhua;
           con= DriverManager.getConnection("jdbc:odbc:lai","","");    
           sql.executeUpdate(temp);       
          
             con.close();
    }
   catch(SQLException ee){}
}
  }不知道为什么，就是红色那一步做不出来，连接不上数据库，怎么改都有问题。不知道问题出在那里了。请各位高手帮帮忙，谢谢！

Answer 1

Statement sql=null; 
sql为空呀,你要创建Statement实例
con.createStatement("sql语句");

Answer 2

 Connection  con=DriverManager.getConnection(url,"sa","123"); 
//    执行SQL
        Statement stmt= con.createStatement();
        ResultSet result=stmt.executeQuery(ls_1); //返回结果
     看懂了么？？？

Answer 3

Statement的executeQuery方法，不能直接用sql 调用的，而且sql是参数的

Answer 4

con= DriverManager.getConnection("jdbc:odbc:lai","","");  
//得到连接后给Statement 付值才
        Statement stmt= con.createStatement(); 
//付值才能sql.executeUpdate(temp),不然sql一直是个空值
        sql.executeUpdate(temp);

Answer 5

Class.forName(Driver_name);
Connection conn=DriverManager.getConnection("jdbc:odbc:lai","","");  
PreparedStatement pstmt=conn.prepareStatement(String sql);
pstmt.executeUpdate();