注解：

1. @Insert：添加
2. @Update：修改
3. @Delete：删除
4. @Select：查询
5. @Result：实现结果集封装
6. @Results：可以和 @Reslult 一起使用，封装多个结果集
7. @One：实现一对一和多对一的结果集封装
8. @Many：实现一对多结果集封装

MyBatis 注解不能实现动态SQL 

使用：

1. SqlMapConfig.xml 配置文件

   <mappers><!-- 第一种方式：class引入接口,只能引入一个接口--><mapper class="com.mybatis.Dao.TeacherDao"/><!-- 第二种方法:针对包下边的所用接口--><package name="com.mybatis.Dao"/>
   </mappers>

2. 编写注解：
   1. 增删改查：

      java">@Select("select * from user")
      <!--结果映射集  字段和数据库的字段一一对应-->
      @Results(id = "userMap" ,value = {@Result(property = "id",column = "id"),@Result(property = "username",column = "username"),@Result(property = "birthday",column = "birthday"),@Result(property = "sex",column = "sex"),@Result(property = "address",column = "address")
      })
      List<User> findAll();@Select("select * from user where id = #{id}")
      @ResultMap(value = "userMap")
      List<User> findById(Integer id);@Select("select * from user where username = #{name}")
      @ResultMap(value = "userMap")
      List<User> findByName(String name);@Update("update user set username = #{username},birthday = #{birthday},sex = #{sex},address = #{address} where id = #{id}")
      int update(User user);@Delete("delete from user where  id = #{id}")
      int delete(Integer id);@Insert("insert into user (username,birthday,sex,address) value(#{username},#{birthday},#{sex},#{address})")
      int insert(User user);

3. 多对一注解查询：
   1. 立即加载：

      java">@Select("select student.*,teacher.Tname from student left join teacher on student.t_id = teacher.id")
      @Results(id = "StudentMap",value = {@Result(property = "id",column = "id"),@Result(property = "Sname",column = "Sname"),@Result(property = "sex",column = "sex"),@Result(property = "age",column = "age"),@Result(property = "t_id",column = "t_id"),@Result(property = "teacher.Tname",column = "Tname")
      })
      List<Student> SelectStudentTeacher();

   2. 延迟加载：

      java">@Select("select * from student")
      @Results(id = "StudentMap",value = {@Result(property = "id",column = "id"),@Result(property = "Sname",column = "Sname"),@Result(property = "sex",column = "sex"),@Result(property = "age",column = "age"),@Result(property = "t_id",column = "t_id"),@Result(property = "teacher",column = "t_id",one = @One(select = "com.mybatis.Dao.TeacherDao.findTeacherById"))
      })
      List<Student> SelectStudentTeacher();//teacherDao接口
      @Select("select * from teacher where id = #{t_id}")
      List<Teacher> findTeacherById(Integer t_id);

   3. 一对多注解查询：

      java">@Select("select * from teacher")
      @Results(id = "teacherMap",value = {@Result(property = "id",column = "id"),@Result(property = "Tname",column = "Tname"),@Result(property = "student",column = "id",many = @Many(select = "com.mybatis.Dao.StudentDao.selectStudentByTeacherId",fetchType = FetchType.LAZY))    //延迟加载
      })
      List<Teacher> selectTeacherStudent();//studentDao接口
      @Select("select * from student where t_id = #{id}")
      List<Student> selectStudentByTeacherId(Integer id);