How to implement different databases for different list items?

Right now, I have a simple note taking app that uses listview and a database to display items that the user has entered into the app.

What I'm trying to do is implement "sub-databases" for each item... more or so like 'categories' or 'folders', where the user can make notes about specific notes (notes within a note).

How can I go about doing this? I also want to contain the speed and performance of the app, so I don't want to create multiple databases and just have the app search for the value.

I'm new to SQL, Android, and Java (programming in general), so a lot of guidance would be nice.

What I'm thinking is maybe passing the ID of whatever list item is picked into another method or maybe even activity, and then storing the values of whatever the person enters in that category as value + "ID" and then having the method to display the values just ignore the values that aren't pertinent to the current screen? Or maybe just making multiple columns?

Thanks in advance!