第二步，Mapper继承常用的数据库增删改查

package com.tj.reggie.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.tj.reggie.entity.Users;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface UsersMapper extends BaseMapper<Users> {
    //继承BaseMapper常用的增删改查
}