-spring boot integrates mybatis using annotations to implement
spring boot and mybatis have been integrated normally, and annotations are used when using queries (the project does not have any XML files)

@Mapper
@Table(name = "t_user")
public interface UserMapper {

    @Select("select * from t_user where user_id = #{id}")
      public User findUserById(@Param("id") String id);
}

I don’t know why in this way, only a few attributes will be filled with values, and the results of other attribute queries are null

#But if I write

 @Results({
 @Result(column = "user_id",property = "userId"),
            @Result(column = "username",property = "username"),
            @Result(column = "pass",property = "pass"),
            @Result(column = "phone_number",property = "phoneNumber")
})

It will be completely correct, every attribute has a value
Question 1: Why do some attributes have a value and some attributes have no value?
Question 2: I can’t write every query statement like this, so there will be a lot of repeated @Result parts. Are there any annotations to implement the corresponding relationship internally? , there is no need to write @ Result?