A simple where clause in flutter/firebase database

Question

Today I started experimenting with Firebase Live database. Maybe I'm thinking too much in sql terms. But what I want to do is get a record from my database where a value equals a variable with flutter. My table looks like this:

What I'm trying to achieve is something like this:

FirebaseDatabase.instance.reference().child('users').where('User_id', 1508)

Like I said. I'm a complete beginner when it comes to Live Databases. I hope someone can help me with this issue I'm having.

Kind regards, Namanix

It was? I'm sorry. I want to get a record out of the Firebase database with a specific user_id but i have no idea how — Kevin Walter, Apr 11 '18 at 14:12
Usually you'll want to set that `User_id` as the key of your object. Instead of a GUID. So that you can do `.child('users/42')` instead of a query. — Rémi Rousselet, Apr 11 '18 at 14:34

score 8 · Answer 1 · answered Oct 03 '18 at 23:23

8

According to firstore docs

Firestore.instance
  .collection('talks')
  .where("topic", isEqualTo: "flutter")
  .snapshots()
  .listen((data) =>
    data.documents.forEach((doc) => print(doc["title"])));

answered Oct 03 '18 at 23:23

Nomi

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This seems correct, but calling those "docs" is very generous. The Firebase documentation for Dart/Flutter is so bad that I question if soon they'll drop support altogether... I'm scared to proceed with this project. If they were more serious about dart/flutter support wouldn't they give more attention to their docs? – Tyler Biscoe Aug 30 '19 at 02:38
1

You are talking about the FirebaseStore but question is related to the real-time-database. – Sohaib Aslam Feb 03 '20 at 07:19
how can we use your code in widgets like whether to wrap in future builder and what to use `QuerySsnapshots` or `DocumentSnapshot` – Mithson Sep 24 '21 at 16:29

Shady Aziza · Answer 2 · 2018-04-11T14:24:31.060

2

If you have the user id in a variable for example called:

String uid = currentUser.uid;

then you can do the following:

FirebaseDatabase.instance.reference().child('users/$uid')

Update I think this is what you are asking about

FirebaseDatabase.instance
                    .reference().child("users")
                    .orderByChild("User_id")
                    .equalTo($this.userId)

edited Apr 11 '18 at 14:24

answered Apr 11 '18 at 14:14

Shady Aziza

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That won't work in my case. The user_id is in the record. The id in users/$uid is generated by firebase and not used by me. – Kevin Walter Apr 11 '18 at 14:16
I am confused. You do have it in your auth object – Shady Aziza Apr 11 '18 at 14:17
You literally said this `But what I want to do is get a record from my database where a value equals a variable with flutter` – Shady Aziza Apr 11 '18 at 14:18
1

The user_id that I want to search the database with is 1 deeper. users/-L9ozsSf-rtHDfwgHRrm/$uid. – Kevin Walter Apr 11 '18 at 14:19
If I understand you correctly then I think you are looking for orderByChild, I updated the answer – Shady Aziza Apr 11 '18 at 14:24
I mean equalTo, orderByChild is not important here – Shady Aziza Apr 11 '18 at 14:28
Hmmm i just tried it but still getting back null values. This is really hard to get my head around after 10+ years of SQL... `dynamic test = await FirebaseDatabase.instance.reference().child('users').equalTo('1508').once().then((DataSnapshot snapshot){ print(snapshot.value); });` – Kevin Walter Apr 11 '18 at 14:30
You need to add the key "User_id", else how will it know what equals to what – Shady Aziza Apr 11 '18 at 14:30
I mean `FirebaseDatabase.instance.reference().child("users/User_id").equalTo(this.uid)` – Shady Aziza Apr 11 '18 at 14:31
How do i add a key to this line of code? Or do i need to add it in the database? – Kevin Walter Apr 11 '18 at 14:31
Still getting back null values. `FirebaseDatabase.instance.reference().child('users/User_id').equalTo('1508').once().then((DataSnapshot snapshot){print(snapshot.value);});` – Kevin Walter Apr 11 '18 at 14:33
3

It'd be much more performant to set `user_id` as key of the object instead of a guid. – Rémi Rousselet Apr 11 '18 at 14:34
I've just set the object key as the user_id and now it all works fine. Thank you for the help! – Kevin Walter Apr 11 '18 at 14:46

krishnaacharyaa · Answer 3 · 2023-01-17T20:27:08.927

@override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
          child: FutureBuilder<QuerySnapshot>(
        future: FirebaseFirestore
                .instance
                .collection('users') 
                .where("user_id", isEqualTo: FirebaseAuth.instance.currentUser!.uid)//  Your where condition here
                .get(), 
        builder: (_, snapshot) {
          if (snapshot.hasError) return Text('Error = ${snapshot.error}');
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const Text("Loading");
          }
          return ListView(
              children: snapshot.data!.docs.map((DocumentSnapshot document) {
            Map<String, dynamic> data = document.data()! as Map<String, dynamic>;
            return ListTile(
              title: Text(data['avatar']), //  Your valid data here
            );
          }).toList());
        },
      )),
    );
  }

Also refer: How to use StreamBuilder and FutureBuilder for single and multiple documents

A simple where clause in flutter/firebase database

3 Answers3