这是我查询的那个方法,执行查询。可是不行,是不是我下面的的查询语句有问题:
String querySql="SELECT student.student_ID,student_name,course_name,result" +
                     " FROM student,course,xuanxiu" +
                     "WHERE student.student_ID=xuanxiu.student_ID " +
                     "ANDxuanxiu.course_ID=course.course_ID";
public void search()
    {
        //创建查询条件面板
        final JTextField txtNumber=new JTextField();            
        txtNumber.addActionListener(tfl);        
        JTextField txtName=new JTextField();
        txtName.addActionListener(tfl);        
        JPanel sp=new JPanel();
        sp.setLayout(new GridBagLayout());
        LayoutUtil.add(sp,GridBagConstraints.HORIZONTAL,
                       GridBagConstraints.CENTER,100,0,0,0,1,1,new JLabel("学生编号"));
        LayoutUtil.add(sp,GridBagConstraints.HORIZONTAL,
                       GridBagConstraints.CENTER,100,0,0,1,1,1,txtNumber);
        LayoutUtil.add(sp,GridBagConstraints.HORIZONTAL,
                       GridBagConstraints.CENTER,100,0,0,2,1,1,new JLabel("学生姓名"));
        LayoutUtil.add(sp,GridBagConstraints.HORIZONTAL,
                       GridBagConstraints.CENTER,100,0,0,3,1,1,txtName);
        //txtName获得输入焦点
        SwingUtilities.invokeLater(new Runnable()
        {
                public void run()
                {
                    txtNumber.requestFocus();
                }            
            });    
        //创建查询对话框
        String[] options = { "确定", "取消"}; 
        int result = JOptionPane.showOptionDialog( 
             father,   // 父组件
             sp, // 查询条件面板
             "查询条件", // 对话框标题 
             JOptionPane.DEFAULT_OPTION, // 选项类型 
             JOptionPane.QUESTION_MESSAGE, // 消息类型 
             null,   //图标
             options, // 按钮
             options[0]  // 缺省按钮 
         ); 
        if(result==JOptionPane.OK_OPTION)
        { //用户按下确定按钮
             String querySql="SELECT student.student_ID,student_name,course_name,result" +
                     " FROM student,course,xuanxiu" +
                     "WHERE student.student_ID=xuanxiu.student_ID " +
                     "ANDxuanxiu.course_ID=course.course_ID";
             SqlUtil.readDBToTable(con,querySql,model,dataType);
        }
    }