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);

}

}