在更新时先判断传入的参数是否为null或空串以实现条件更新

 @Update({
            "<script> ",
            "update tb_user_info set ",
            "<if test = "uprofession != null"> ",
            "uprofession=#{uprofession}, ",
            "</if> ",
            "<if test = "umajor != null"> ",
            "umajor=#{umajor}, ",
            "</if> ",
            "<if test = "directionOfStudy != null"> ",
            "directionOfStudy=#{directionOfStudy}, ",
            "</if> ",
            "update_time=CURRENT_TIMESTAMP ",
            "WHERE user_id=#{user_id}",
            "</script>"
            })
    void updateUserInfo(
                        @Param("user_id") int user_id,
                        @Param("uprofession") String uprofession,
                        @Param("umajor") String umajor,
                        @Param("directionOfStudy") String directionOfStudy
                        );