如何从Firebase参考中将孩子放在第一层？ （浅查询）

Question

I have a Firebase Database structure that looks like this:

/users
    - abc001
        - name: "Harry Watson"
        - credentials: 
            - email: "h.watson@yahoo.com"
    - abc002
        - name: "Jason Polakow"
            - credentials: 
                - email: "j.polakow_1@gmail.com"
    - abc003
        - name: "Madeleine Février"
        - credentials: 
            - email: "mad_fev@gmail.fr"
    - ...

I would like to get all children on the first layer, eg:

- abc001
- abc002
- abc003
...

• I don't know how to do this. As far as I know, a value event would also trigger for every child of every child (second and third layer).
  
• A childAdded event is also not the right choice, because I only want to receive the data once (I don't want to listen for data changes/child added, ...).
  
• A single-event of childAdded only triggers once and returns the first child ( abc001 ).

Could you help me out?

Thanks in advance.

Answer 1

This is not possible with your data structure. Firebase Realtime Database doesn't have "shallow queries". When you listen to a location, you get all of its nested data all of the time. There are no plans to change this.

You could instead create a new location in your database that contains just the data you're looking for. It's common to duplicate data like this in NoSQL databases. You just have to remember to keep all the duplicates up to date any time one of them needs to change.