How to save data on top of the already saved data in Firebase?

Question

I am saving some data in FirebaseDatabase under a child as a key:value pair.

The problem is that data is getting saved as pushed, like if data1 is saved already than data2 will get saved below it. I want to save it above this already saved data.

Here is the data structure:

- branch
    - child
        - uniqueKey1: data1
        - uniqueKey2: data2

I am saving the data using this code:

String key = mDatabase.child("branch").child("child").push().getKey();

mDatabase.child("branch").child("child").child(key).setValue(data);

What I want is the structure below:

- branch
    - child
        - uniqueKey2: data2
        - uniqueKey1: data1

How to save the newly added data above the already saved data? Please let me know.

score 1 · Answer 1 · answered Dec 11 '16 at 19:29

1

I don't think the order in which you save data is important as long as you have a strategy to retrieve it correctly in your order of choice. Firebase provides API to retrieve data ordered by either key or value.

Work with Lists of Data on Android

If you just want to retrieve the record first which was added last, you can put a timestamp that accompanies your data. There are also methods that gets you last record of a collection.

answered Dec 11 '16 at 19:29

jaibatrik

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Okay! But is there a way to save data in the order I want? – Hammad Nasir Dec 11 '16 at 19:30
I think what you can do is to replace the `child` node completely and assign it an array in which children are arranged in the order that you want. – jaibatrik Dec 11 '16 at 19:43
If I use `timestamp`, then how to retrieve the data in descending form? Like from the last `timestamp` saved? – Hammad Nasir Dec 11 '16 at 20:12

score 1 · Accepted Answer · edited May 23 '17 at 12:01

1

In your firebase database, childs in a node are ordered in alphabetical order, no matter which order you save them. If you want to retrieve them later in some specific order, let's say order by date added, you might want to create a timestamp reference.

Check here: How to sort value inside a Firebase child to the rest?

Edit: a lot of answers and edited questions while writing my answer, but as others mentioned you should not worry about the order you see the data in the database, you should only care to provide the right structure to retrieve the data correctly. As I said, in the DB the childs are ordered in alphabetical order so if you insist on ordering it by date added you should figure out a way to update the key accordingly and then update the whole node.

edited May 23 '17 at 12:01

Community

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answered Dec 11 '16 at 19:51

Raul Lopez

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Okay! Then how to retrieve in descending order if I'm saving the `timestamp` too? I mean the `timestamp` which is last one first? – Hammad Nasir Dec 11 '16 at 20:05
Check this answer, I think it's exactly what you need. http://stackoverflow.com/questions/34156996/firebase-data-desc-sorting-in-android – Raul Lopez Dec 11 '16 at 20:17
hey, I have accepted this answer but I'm still having a problem... I'm using this to save the name of those who followed me and the problem is that I'm saving it under the `uid` of the one who followed me and now when I have to retrieve it, I'm unable to understand how to get the `uid` of the user who has followed me. What should I do? – Hammad Nasir Dec 14 '16 at 05:54

score 0 · Answer 3 · answered Dec 11 '16 at 19:08

0

What you are trying to do is update data1. Then what you have to do is,
Get reference of the node you want to update.

DatabaseReference ref = mDatabase.child("branch").child("child").child("data1");

then update the child node. I'm assuming there is a child name under data1, whose value is 'Foo'. And now you want to update it 'Bar'.

Hashmap<String, String> map = new Hashmap();
map.put("name","Bar");

ref.updateChildren(map);

This is how you update a node. If you want to completely replace the node, then you can delete the node and by calling removeValue() method and pushing the data again!.

answered Dec 11 '16 at 19:08

Nishanth Sreedhara

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No. I am not trying to remove or update anything. I just have to add `data2` above `data1`. That's all! – Hammad Nasir Dec 11 '16 at 19:13
I'm not getting. Could you explain what you are trying to achieve specifically? – Nishanth Sreedhara Dec 11 '16 at 19:14
I'm really sorry about wrong code and structure in the question. Please see the edited question. – Hammad Nasir Dec 11 '16 at 19:15
Do you want to update data1? What is data1? What value does it contain?Be specific. – Nishanth Sreedhara Dec 11 '16 at 19:17
I hope the edited question will make it clear now. Please have a look again, – Hammad Nasir Dec 11 '16 at 19:19
It is much better. The previous one didn't make any sense ;)... "How to save the newly added data above the already saved data?" Are you trying to update the `uniqueKey1`'s value ? – Nishanth Sreedhara Dec 11 '16 at 19:21
I'm not trying to update or remove anything. I'm adding new data and I just want that the new added data should appear above the data already saved. – Hammad Nasir Dec 11 '16 at 19:22
Ok, now I understood. But why does it matters how it is stored in the database? If you want to display user the recently created data first, then you must work on the way you form your query. – Nishanth Sreedhara Dec 11 '16 at 19:31

How to save data on top of the already saved data in Firebase?

3 Answers3