Search firebase realtime database base on 6 digit in front of the child data, i want to query data between two numbers (dates)

Question

Is there possible to search database on 6 first digits from the Realtime Database, something like I search for 211010 and the data in range/having the 211010 in front of it will show up like 211010XXXXXXX, 211010XXXXXXX, I want to query data between two numbers (dates).

the 211010 was a date 2021-10-10

Answer 1

You might be tempted to use a query that looks like this:

DatabaseReference db = FirebaseDatabase.getInstance().getReference();
DatabaseReference pendingRef = db.child("Pending");
Query queryByKey = pendingRef.orderByKey().startAt("211010");

But this will not provide the expected results. Why? Because of the reason provided by @FrankvanPuffelen in the following answer:

• Firebase OrderByKey with startAt and endAt giving wrong results

So to solve this, the best option that you have is not to use only numerical values for the keys. So a simple solution would be to prefix the keys with a constant String. So the corresponding query should look like this:

Query queryByKey = pendingRef.orderByKey().startAt("*211010").endAt("*211010" + "\uf8ff");
//                                                                 

And the keys in the database should look like this:

Firebase-root
  |
  --- *211010...
  |
  --- *211010...
  |
  --- *211010...

Edit:

I just took the following example:

{
  "Pending" : {
    "2110101" : {
      "name" : 1
    },
    "2110102" : {
      "name" : 2
    },
    "2110103" : {
      "name" : 3
    },
    "2110114" : { //It's 21-10-11 and not  //It's 21-10-10
      "name" : 4
    },
  }
}

Using the following query (no * added before the number):

Query queryByKey = pendingRef.orderByKey().startAt("211010").endAt("211010" + "\uf8ff");

I get the following result:

name: 1
name: 2
name: 3
name: 4

So I get all results. However, when I use:

{
  "Pending" : {
    "*2110101" : {
      "name" : 1
    },
    "*2110102" : {
      "name" : 2
    },
    "*2110103" : {
      "name" : 3
    },
    "*2110114" : { //It's 21-10-11 and not  //It's 21-10-10
      "name" : 4
    },
  }
}

And the following query (with the * added before):

Query queryByKey = pendingRef.orderByKey().startAt("*211010").endAt("*211010" + "\uf8ff");

I only get:

name: 1
name: 2
name: 3

So it works in this case as well.