Online database connect to android app

I try to develop an android app, In this app, users can enter data (for example. emergency blood request) and that data can be seen by all others who are using the app, for that, I have to try to implement an online database in such a way that a row in table for each request

I already implement all UI.....in android sdk. but i stuck with creating database and integrating it in my app

I already tried Microsoft azure and Google cloud but they asks me for credit card details....

I need your suggestions and some tutorials to getting start in.

Are there any free web services that are providing free databases and how can I integrate them into my android.