firebase how to read values until specified length

I want to get the total number count until specified.

this is my database: database picture

I want to count where ticket_status is not served

ex: I want to count until A6, I will count A1 until A5 where the value of ticket_status" is not served. so the final count will be 3.

is there any filtering kind?

I have this code but it just counts all nodes with the value of "not served"

dbref.child("Queue").child(a.value.toString()).orderByChild("ticket_status").equalTo("not served").addValueEventListener(object : ValueEventListener{
                                override fun onDataChange(snap: DataSnapshot) {
                                        val count = snap.childrenCount
                              dbref.child("Student_Queue_Reserve").child(idNumber.toString()).child("people_ahead").setValue((count-1).toString())
                                }
                                override fun onCancelled(error: DatabaseError) {
                                }
                            })

> I want to count until A6, I will count A1 until A5 where the value of ticket_status" is not served. So the final count will be 3.

There is no way you can do that in the Realtime Database because queries can only order/filter on a single property. There are cases in which you can combine the values you want to filter into a single property. For example, please check my answer below:

• https://stackoverflow.com/questions/48340925/how-to-sort-firebase-records-by-two-fields-android/48343592#48343592

If you're allowed to change the database schema, then you should consider denormalizing the data. So a structure like below will do the trick:

db
|
--- Queue
     |
     --- Accounting Office
           |
           --- served
           |    |
           |    --- A1
           |    |   |
           |    |   --- serving_token: "A001"
           |    |   |
           |    |   --- ticket_status: "served"
           |    |
           |    --- A2
           |        |
           |        --- serving_token: "A002"
           |        |
           |        --- ticket_status: "served"
           |
           --- not served
                |
                --- A3
                |   |
                |   --- serving_token: "A003"
                |   |
                |   --- ticket_status: "not served"
                |
                --- A4
                |   |
                |   --- serving_token: "A004"
                |   |
                |   --- ticket_status: "not served"
                |
                --- A5
                |   |
                |   --- serving_token: "A005"
                |   |
                |   --- ticket_status: "not served"
                |
                --- A6
                    |
                    --- serving_token: "A006"
                    |
                    --- ticket_status: "not served"

Now you can query the "not served" node, using a combination of Query#orderByKey() and Query#endAt(java.lang.String)

db.child("Queue").child("Accounting Office").child("not served").orderByKey().endAt("A6");

You can try this approach without query:

ArrayList servedArray ;
ArrayList notServedArray ;

• get a data snapshot
• loop through snapshot
• if value == "served" >> add to servedArray
• else if value equal == "not served" add to notServedArray

And for count you can use :

servedArray.size
notServedArray.size