Firebase: Query to exclude data based on a condition
I think I've found the solution and this is more of how the database should be designed and actually now I understood the intention behind Firebase guideline
https://firebase.google.com/docs/database/android/structure-data
Original Design:
{
child1: {
"user": {
"id": "id1",
"name": "puf"
}
},
child2: {
"user": {
"id": "id2",
"name": "abe"
}
},
child3: {
"user": {
"id": "id1"
"name": "puf"
}
}
}
Updated Design:
So apart from the storing the id and name of the user, we should also store a node with the id itself as the key and mark it to true
{
child1: {
"user": {
"id": "id1",
"name": "puf"
"id1": true
}
},
child2: {
"user": {
"id": "id2",
"name": "abe"
"id2": true
}
},
child3: {
"user": {
"id": "id1"
"name": "puf"
"id1": true
}
}
}
With the updated design, if i execute ref.orderByChild('user/id1').equalTo(true)
I would get output as Child1 and Child 3
and if i execute ref.orderByChild('user/id1').equalTo(null)
,
I would get Child2 as the output
In the Firebase Query model you can not filter for inequality to a value.
But you can test for the absence of any value (essentially: the absence of a property). For example with this data model:
{
child1: {
"user": {
"id": 1,
"name": "puf"
}
},
child2: {
"user": {
"id": 2,
"name": "abe"
}
},
child3: {
"user": {
"id": 3
}
}
}
I can query for children without a user/name
property with:
ref.orderByChild('user/name').equalTo(null)
Which leads to the only child that doesn't have a name:
child3
Feel free to play with my jsbin to see if you get further: http://jsbin.com/liyibo/edit?js,console
Update: I knew I'd answered this before, but couldn't find it earlier. Here's the dupe: is it possible query data that are not equal to the specified condition?. It looks like I have a mistake in there, since clearly I'm testing for the absence of a property in the above code.