text: create table roles(
      role_id int primary key auto_increment,
      role_name varchar(20) not null
  );
  insert into roles (role_name) values ('管理员'), ('普通用户');
  
  create table users(
      user_id int primary key auto_increment,
      username varchar(20) not null unique,
      password char(32) not null,
      role_id int not null default 2,
      foreign key(role_id) references roles(role_id)
  );
  insert into users (username, password, role_id) values ('admin', '202cb962ac59075b964b07152d234b70', 1), ('gerald', '202cb962ac59075b964b07152d234b70', 2);