How to fetch all parent nodes with similar child nodes on Firebase database Android?

Question

Screen shot of my Database

I would like to query my database by returning the names of all parents nodes which have certain similar child nodes.

I am already fetching the name of one parent with respect to it's child, but I want to fetch the name of all parents with similar child value.

Suppose, I want to get the names of the Hotels which have the similar child node value of 2000 and have a Rating of 3-star.

final List<String> hotelNames = new ArrayList<String>();
final Query userQuery = FirebaseDatabase.getInstance().getReference().child("F-5").orderByChild("HotelTypeTwo");

userQuery.equalTo(varX).addListenerForSingleValueEvent(
        new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot foodSnapshot: dataSnapshot.getChildren()) {


                    hotelNames.add(foodSnapshot.getKey());


                    for (int i=0;i < hotelNames.size();i++)
                    {
                        Log.i("Value of element "+i,hotelNames.get(i));

                    }

                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        }
);

Please add your database structure and indicate the exact data that you want to get. — Alex Mamo, May 10 '19 at 09:11
I have shared the screenshot of my Database. I have also edited the question for required data. — Raja Shahroze, May 10 '19 at 09:16
So you want to get all hotels where `HotelTypeTwo` is equal to `Desi` and the result you expect according to your screenshot should be: `Islamabad Mariott Hotel` and `Islamabad Hotel`, right? — Alex Mamo, May 10 '19 at 09:21
Exactly! but please add another condition, where "Rating" is equal to "3-Star" as well. — Raja Shahroze, May 10 '19 at 09:24
Currently you cannot use two where conditions. Will be an answer helpful with only one condition? — Alex Mamo, May 10 '19 at 09:28
@AlexMamo that would be highly appreciated. Highly obliged by your assistance. — Raja Shahroze, May 10 '19 at 09:29

score 2 · Accepted Answer · answered May 10 '19 at 09:44

So to get all hotels where HotelTypeTwo is equal to Desi and get according to your screenshot as results: Islamabad Hotel and Islamabad Mariott Hotel, please use the follwing lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference fRef = rootRef.child("F-5");
Query query = fRef.orderByChild("HotelTypeTwo").equalTo("Desi");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String hotelName = ds.getKey();
            Log.d(TAG, hotelName);
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
    }
};
query.addListenerForSingleValueEvent(valueEventListener);

The result in your logcat will be:

Islamabad Hotel
Islamabad Mariott Hotel

Unfortunately, querying on multiple properties is not permitted in Firebase. A workaround can be my answer from the following post:

How to sort Firebase records by two fields (Android)

However, in Firestore compound queries are permitted:

citiesRef.whereEqualTo("state", "CO").whereEqualTo("name", "Denver");

How to fetch all parent nodes with similar child nodes on Firebase database Android?

1 Answers1