How to get children with a value not equal to 0

Question

Consider the following JSON format in Firebase database -

"root":
{
    "question":
    {
        "1":
        {
            "category":"A",
            "replies":0
        },
        "2":
        {
            "category":"B",
            "replies":1
        },
        "3":
        {
            "category":"B",
            "replies":0
        },
        "4":
        {
            "category":"C",
            "replies":2
        }
    }
}

For getting all questions with replies = 0, I do,

Query query = rootReference.child("question").orderByChild("replies").equalTo(0);

which works perfectly.

But what should I do if I want those questions with replies not equal to 0 ?

Try using the != syntax instead of .equalTo – Nero Nov 24 '17 at 17:26 — Nero, Nov 24 '17 at 17:26

score 3 · Accepted Answer · answered Nov 24 '17 at 17:45

3

Reading the documentation, I see no notEqualTo() method or any other way to "negate" a query. However, since you're already calling .orderByChild("replies"), you could perhaps use this:

Query query = rootReference.child("question").orderByChild("replies").startAt(1);

answered Nov 24 '17 at 17:45

Ben P.

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that I guess will leave others which are !=0&&!=1 – vikas kumar Nov 24 '17 at 17:48
@vikaskumar documentation for `startAt()` says "return child nodes with a value greater than or equal to the given value", so the only problem arises if negative values are possible in OP's data set. – Ben P. Nov 24 '17 at 17:56
then I guess this should be the right way to do it. as replies cannot be negative in ideal conditions. – vikas kumar Nov 24 '17 at 17:58
Great answer Ben! – Frank van Puffelen Nov 24 '17 at 18:12

score 0 · Answer 2 · answered Nov 24 '17 at 17:45

0

Firebase currently supports only positive operations, not the negation. so you may want to retrieve all the data and then filter it locally.

Here is full answer

answered Nov 24 '17 at 17:45

vikas kumar

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Prashant Saini · Answer 3 · 2017-11-24T17:56:32.827

Actually Firebase doesn't provide any method to exclude some results like you are seeking here.

However, you can modify your JSON like this & then use following query:

// add a different key for all replies = 0, & another different key for non-zero replies
"root":
{
    "question":
    {
        "1":
        {
            "category":"A",
            "replies":0,
            "key2":"someOtherKey"
        },
        "2":
        {
            "category":"B",
            "replies":1,
            "key1":true
        },
        "3":
        {
            "category":"B",
            "replies":0,
            "key2":"someOtherKey"
        },
        "4":
        {
            "category":"C",
            "replies":2,
            "key1":true
        }
    }
}

// now you can use this query to get all non-zero-replies results
// it will give you child 2, 4
Query query = rootReference.child("question").orderByChild("key1").equalTo(true);

// to get all zero-replies childs, use this
Query query = rootReference.child("question").orderByChild("key1").equalTo(null);

How to get children with a value not equal to 0

3 Answers3