课堂练习（mysql--java）

1.查询所有学生记录，包含年级名称

DAO实现类

@Override
    public List<Student> selectStudents() throws Exception {
        List<Student> list=new ArrayList<Student>();
        String sql="select * from Student,grade where Student.gradeid=grade.gradeid";
        ResultSet exe = executeQuery(sql);
        if (exe!=null) {
            while (exe.next()) {
                Student stu=new Student();
                grade grade=new grade();
                stu.setStudentname(exe.getString("studentname"));
                stu.setSex(exe.getInt("sex"));
                grade.setGradename(exe.getString("gradename"));
                stu.setGrade(grade);
                list.add(stu);
            }
        }
        closs();
        return list;
    }

entity

private int stduentNo;
    private String loginpwd;
    private String studentname;
    private int sex;
    private int gradeid;
    private String phone;
    private String address;
    private grade grade=new grade();

2.查询S1年级下的学生记

DAO实现类

@Override
    public grade selegrade(String gradename) throws Exception {
        grade grade=new com.myschool.entity.grade();
        String sql="select * from Student,grade where Student.gradeid=grade.gradeid and gradename=?";
        ResultSet rs = executeQuery(sql, gradename);
        if (rs!=null) {
            while (rs.next()) {
                grade.setGradename(rs.getString("gradename"));
                Student stu=new Student();
                stu.setStudentname(rs.getString("studentname"));
                grade.getListStudents().add(stu);
            }
        }
        closs();
        return grade;
    }

entity

private int gradeid;
    private String gradename;
    public List<Student> listStudents=new ArrayList<Student>();