Help with creating a push notification from database

I am new to Android development and would like to build an app which would allow the users to manage and receive alerts from updates of my database. For example, let's say I am a produce wholesaler and I update my inventory database throughout each day. I want to provide an app to my network of retailers which would allow them to set up/manage/receive alerts when our inventory database is updated. Some might want to know when lemons are updated but not oranges. Any help pointing my in the right direction would be greatly appreciated!