How can I check If the data already exists in the database?

Question

I'm developing a reservation mobile app wherein when I click the checkAvailability, it will check if the data already exists in the database. My problem is that I don't know how to access since the key is randomly generated. There is a lot of similar questions to mine but no solutions has been working for me.

Firebase Database(Screenshot):

btnAvailability.setOnClickListener

btnAvailability.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Query userQuery = database.getInstance().getReference().child("Requests")
                    .orderByChild("order/0");
            userQuery.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    String type = dataSnapshot.child("checkIn").getValue().toString();
                    String type2 = dataSnapshot.child("productName").getValue().toString();
                    if(type.equals(checkInTV.getText().toString()) && type2.equals(beach_name.getText().toString())) {
                        Toast.makeText(details.this, "Not Available", Toast.LENGTH_SHORT).show();
                    }else
                    {
                        Toast.makeText(details.this, "Available", Toast.LENGTH_SHORT).show();
                    }

                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {

                }
            });

        }
    });

Answer 1

Finally found a solution on my problem.

        btnAvailability.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Query userQuery = database.getInstance().getReference().child("Requests")
                    .orderByChild("order/0/checkIn").equalTo(checkInTV.getText().toString());
            userQuery.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    for (DataSnapshot snapshot: dataSnapshot.getChildren()) {
                        String type2 = snapshot.child("order/0/productName").getValue().toString();
                        if(type2.equals(beach_name.getText().toString())) {
                            Toast.makeText(details.this, "Not Available", Toast.LENGTH_SHORT).show();
                        }
                        else {
                            Toast.makeText(details.this, "Available", Toast.LENGTH_SHORT).show();
                        }
                    }
                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                    throw databaseError.toException();
                }
            });

        }
    });

Answer 2

From the looks of it, you're trying to check of there is a child that has order/0 with a specific checkIn and productName under Requests. In your current data structure you can do that with:

Query userQuery = database.getInstance().getReference().child("Requests")
        .orderByChild("order/0");
userQuery.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        for (DataSnapshot snapshot: dataSnapshot.getChildren()) {
            String type = snapshot.child("checkIn").getValue().toString();
            String type2 = snapshot.child("productName").getValue().toString();
            if(type.equals("Saturday, April 20, 2019") && type2.equals("The Mansion")) {
                Toast.makeText(details.this, "Not Available", Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(details.this, "Available", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        throw databaseError.toException()
    }
});

Differences from your code:

• I have a loop inside onDataChange, since a query can have multiple results.
• I hardcoded the date to rule out the problem being caused by the way you input the data in the text view.
• I handle onCancelled, since ignoring errors is just a bad idea.

---

A more efficient way to accomplish the same is to have Firebase do part of the query, like this:

Query userQuery = database.getInstance().getReference().child("Requests")
        .orderByChild("order/0/checkIn").equalTo("Saturday, April 20, 2019");
userQuery.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        for (DataSnapshot snapshot: dataSnapshot.getChildren()) {
            String type2 = snapshot.child("productName").getValue().toString();
            if(type2.equals("The Mansion")) {
                Toast.makeText(details.this, "Not Available", Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(details.this, "Available", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        throw databaseError.toException()
    }
});

In here the change is:

• I moved part of the check into the query, so that Firebase can perform that filter on the server. This means it has to download less data to the client, making it both faster and cheaper.
• You'll still have to filter the second value client-side, since Firebase queries can only order/filter on one property. For more on this, see Query based on multiple where clauses in Firebase.

---

Note that you're querying double nested data. While you can get this to work for a specific order (orders/0 in this example), if you can have multiple orders in a request, Firebase won't be able to query across all of them.

For more on this and a solution, see: Firebase Query Double Nested

I'd also recommend reading my answers about modeling categories, because I have a feeling you'll need this soon: Firebase query if child of child contains a value

Answer 3

While storing data you need make user email id as first parameter so that you can access data based on user.

{"reuest":{"xyz@gmail.com":{"orders":[{"checkin":"21:29"},{"checkin":"2:19"}]},"abc@gmail.com":{"orders":[{"checkin":"21:29"},{"checkin":"2:19"}]}}}