一旦在MySQL数据库中发生更新，就向android发送通知

In my android app a new user initially registers himself with the app then if the user is approved by the admin from back-end then only he will be able to login.Now,what i want is as soon as admin approve the user, a notification should appear in android mobile telling the user that now he can login successfully as he has been approved.I have stored my data in MySQL database in web server.Now i have no idea how to implement this.Any help would really be appreciated.In my android app a new user initially register