alter table sys_user
    add wechat_nick_name varchar(30) null comment '微信昵称';
alter table sys_user
    add balance float null comment '账户余额';
alter table sys_user
    add referrer_id bigint null comment '推荐人ID';
alter table sys_user
    add constraint sys_user_sys_user_user_id_fk
        foreign key (referrer_id) references sys_user (user_id);