blocks|key|2934783|text|使用Firebase's+Query+API时，您可能会尝试这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2934784|//+!!!+THIS+WILL+NOT+WORK+!!!
ref
++.orderBy('genre')
++.startAt('comedy').endAt('comedy')
++.orderBy('lead')++++++++++++++++++//+!!!+THIS+LINE+WILL+RAISE+AN+ERROR+!!!
++.startAt('Jack+Nicholson').endAt('Jack+Nicholson')
++.on('value',+function(snapshot)+{+
++++++console.log(snapshot.val());+
++});|code-block|syntax|javascript|2934785|但正如来自Firebase的@RobDiMarco在评论中所说的：|2934786|2934787|多个orderBy()调用将抛出错误|blockquote|style|CODE|2934788|2934789|2934790|所以我上面的代码将不会在中工作。|BOLD|2934791|我知道有三种方法是可行的。|2934792|1.在服务器上过滤大部分，其余的在客户端完成|2934793|您可以做的是在服务器上执行一个orderBy().startAt()./endAt()，下拉剩余的数据，然后在客户端的JavaScript代码中对其进行过滤。|2934794|ref
++.orderBy('genre')
++.equalTo('comedy')
++.on('child_added',+function(snapshot)+{+
++++++var+movie+=+snapshot.val();
++++++if+(movie.lead+==+'Jack+Nicholson')+{
++++++++++console.log(movie);
++++++}
++});|2934795|2.添加一个组合了要筛选的值的属性。|2934796|如果这还不够好，你应该考虑修改/扩展你的数据，以允许你的用例。例如:您可以将genre%2Blead填充到仅用于此过滤器的单个属性中。|2934797|"movie1":+{
++++"genre":+"comedy",
++++"name":+"As+good+as+it+gets",
++++"lead":+"Jack+Nicholson",
++++"genre_lead":+"comedy_Jack+Nicholson"
},+//...|2934798|您实际上是在以这种方式构建自己的多列索引，并可以使用以下命令进行查询：|2934799|ref
++.orderBy('genre_lead')
++.equalTo('comedy_Jack+Nicholson')
++.on('child_added',+function(snapshot)+{+
++++++var+movie+=+snapshot.val();
++++++console.log(movie);
++});|2934800|大卫·伊斯特写了一个library+called+QueryBase+that+helps+with+generating+such+properties。|2934801|您甚至可以执行相对/范围查询，假设您希望允许按类别和年份查询电影。您将使用以下数据结构：|2934802|"movie1":+{
++++"genre":+"comedy",
++++"name":+"As+good+as+it+gets",
++++"lead":+"Jack+Nicholson",
++++"genre_year":+"comedy_1997"
},+//...|2934803|然后用以下命令查询90年代的喜剧：|2934804|ref
++.orderBy('genre_year')
++.startAt('comedy_1990')
++.endAt('comedy_2000')
++.on('child_added',+function(snapshot)+{+
++++++var+movie+=+snapshot.val();
++++++console.log(movie);
++});|2934805|如果您需要过滤的不仅仅是年份，请确保按降序添加其他日期部分，例如"comedy_1997-12-25"。这样，Firebase对字符串值进行的字典序排序将与按时间顺序排序相同。|2934806|属性中的值的这种组合可以与两个以上的值一起使用，但您只能对复合属性中的最后一个值进行范围筛选。|2934807|它的一个非常特殊的变体是由GeoFire+library+for+Firebase实现的。这个库将一个位置的纬度和经度组合成一个所谓的Geohash，然后可以用它在Firebase上进行实时范围查询。|2934808|3.以编程方式创建自定义索引|2934809|另一种选择是做我们在添加这个新的查询API之前都做过的事情:在不同的节点中创建一个索引：|2934810|++"movies"
++++++//+the+same+structure+you+have+today
++"by_genre"
++++++"comedy"
++++++++++"by_lead"
++++++++++++++"Jack+Nicholson"
++++++++++++++++++"movie1"
++++++++++++++"Jim+Carrey"
++++++++++++++++++"movie3"
++++++"Horror"
++++++++++"by_lead"
++++++++++++++"Jack+Nicholson"
++++++++++++++++++"movie2"|2934811|可能还有更多的方法。例如，此答案突出显示了另一个树形自定义索引：https://stackoverflow.com/a/34105063|2934812|2934813|如果这些选项对你都不起作用，但你仍然想将数据存储在Firebase中，你也可以考虑使用它的Cloud+Firestore+database。|2934814|Cloud+Firestore可以在一个查询中处理多个相等过滤器，但只能处理一个范围过滤器。在幕后，它本质上使用相同的查询模型，但它像是自动为您生成复合属性。请参阅compound+queries上的Firestore文档。|2934815|entityMap|0|LINK|mutability|MUTABLE|url|https://www.firebase.com/docs/beta/queries/web.html|1|https://github.com/davideast/Querybase|2|https://github.com/firebase/geofire-js|3|https://en.wikipedia.org/wiki/Geohash|4|https://stackoverflow.com/a/34105063|5|https://firebase.google.com/docs/firestore|6|https://firebase.google.com/docs/firestore/query-data/queries#compound_queries^0|2|K|0|0|0|0|0|2|9|0|0|0|2|A|0|0|0|F|S|0|0|0|0|0|0|0|A|1V|1|0|0|0|0|0|W|J|0|0|D|S|2|1V|7|3|0|0|0|0|W|10|4|0|0|19|O|5|0|2A|G|6|0^^$0|@$1|2|3|4|5|6|7|2Q|8|@]|9|@$A|2R|B|2S|1|2T]]|C|$]]|$1|D|3|E|5|F|7|2U|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|2V|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|2W|8|@]|9|@]|C|$]]|$1|L|3|M|5|N|7|2X|8|@$A|2Y|B|2Z|O|P]]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|30|8|@]|9|@]|C|$]]|$1|R|3|-4|5|6|7|31|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|32|8|@$A|33|B|34|O|U]]|9|@]|C|$]]|$1|V|3|W|5|6|7|35|8|@]|9|@]|C|$]]|$1|X|3|Y|5|6|7|36|8|@]|9|@]|C|$]]|$1|Z|3|10|5|6|7|37|8|@$A|38|B|39|O|P]]|9|@]|C|$]]|$1|11|3|12|5|F|7|3A|8|@]|9|@]|C|$G|H]]|$1|13|3|14|5|6|7|3B|8|@]|9|@]|C|$]]|$1|15|3|16|5|6|7|3C|8|@]|9|@]|C|$]]|$1|17|3|18|5|F|7|3D|8|@]|9|@]|C|$G|H]]|$1|19|3|1A|5|6|7|3E|8|@]|9|@]|C|$]]|$1|1B|3|1C|5|F|7|3F|8|@]|9|@]|C|$G|H]]|$1|1D|3|1E|5|6|7|3G|8|@]|9|@$A|3H|B|3I|1|3J]]|C|$]]|$1|1F|3|1G|5|6|7|3K|8|@]|9|@]|C|$]]|$1|1H|3|1I|5|F|7|3L|8|@]|9|@]|C|$G|H]]|$1|1J|3|1K|5|6|7|3M|8|@]|9|@]|C|$]]|$1|1L|3|1M|5|F|7|3N|8|@]|9|@]|C|$G|H]]|$1|1N|3|1O|5|6|7|3O|8|@$A|3P|B|3Q|O|P]]|9|@]|C|$]]|$1|1P|3|1Q|5|6|7|3R|8|@]|9|@]|C|$]]|$1|1R|3|1S|5|6|7|3S|8|@]|9|@$A|3T|B|3U|1|3V]|$A|3W|B|3X|1|3Y]]|C|$]]|$1|1T|3|1U|5|6|7|3Z|8|@]|9|@]|C|$]]|$1|1V|3|1W|5|6|7|40|8|@]|9|@]|C|$]]|$1|1X|3|1Y|5|F|7|41|8|@]|9|@]|C|$G|H]]|$1|1Z|3|20|5|6|7|42|8|@]|9|@$A|43|B|44|1|45]]|C|$]]|$1|21|3|-4|5|6|7|46|8|@]|9|@]|C|$]]|$1|22|3|23|5|6|7|47|8|@]|9|@$A|48|B|49|1|4A]]|C|$]]|$1|24|3|25|5|6|7|4B|8|@]|9|@$A|4C|B|4D|1|4E]]|C|$]]|$1|26|3|-4|5|6|7|4F|8|@]|9|@]|C|$]]]|27|$28|$5|29|2A|2B|C|$2C|2D]]|2E|$5|29|2A|2B|C|$2C|2F]]|2G|$5|29|2A|2B|C|$2C|2H]]|2I|$5|29|2A|2B|C|$2C|2J]]|2K|$5|29|2A|2B|C|$2C|2L]]|2M|$5|29|2A|2B|C|$2C|2N]]|2O|$5|29|2A|2B|C|$2C|2P]]]]

Using <a href="https://www.firebase.com/docs/beta/queries/web.html" rel="noreferrer">Firebase's Query API</a>, you might be tempted to try this:
<pre class="lang-js prettyprint-override"><code>// !!! THIS WILL NOT WORK !!!
ref
 .orderBy('genre')
 .startAt('comedy').endAt('comedy')
 .orderBy('lead') // !!! THIS LINE WILL RAISE AN ERROR !!!
 .startAt('Jack Nicholson').endAt('Jack Nicholson')
 .on('value', function(snapshot) { 
 console.log(snapshot.val()); 
 });
</code></pre>
But as @RobDiMarco from Firebase says in the comments:
<blockquote>
multiple <code>orderBy()</code> calls will throw an error
</blockquote>
So my code above will not work.
I know of three approaches that will work.
<h3>1. filter most on the server, do the rest on the client</h3>
What you can do is execute one <code>orderBy().startAt()./endAt()</code> on the server, pull down the remaining data and filter that in JavaScript code on your client.
<pre class="lang-js prettyprint-override"><code>ref
 .orderBy('genre')
 .equalTo('comedy')
 .on('child_added', function(snapshot) { 
 var movie = snapshot.val();
 if (movie.lead == 'Jack Nicholson') {
 console.log(movie);
 }
 });
</code></pre>
<h3>2. add a property that combines the values that you want to filter on</h3>
If that isn't good enough, you should consider modifying/expanding your data to allow your use-case. For example: you could stuff genre+lead into a single property that you just use for this filter.
<pre class="lang-js prettyprint-override"><code>&quot;movie1&quot;: {
 &quot;genre&quot;: &quot;comedy&quot;,
 &quot;name&quot;: &quot;As good as it gets&quot;,
 &quot;lead&quot;: &quot;Jack Nicholson&quot;,
 &quot;genre_lead&quot;: &quot;comedy_Jack Nicholson&quot;
}, //...
</code></pre>
You're essentially building your own multi-column index that way and can query it with:
<pre class="lang-js prettyprint-override"><code>ref
 .orderBy('genre_lead')
 .equalTo('comedy_Jack Nicholson')
 .on('child_added', function(snapshot) { 
 var movie = snapshot.val();
 console.log(movie);
 });
</code></pre>
David East has written a <a href="https://github.com/davideast/Querybase" rel="noreferrer">library called QueryBase that helps with generating such properties</a>.
You could even do relative/range queries, let's say that you want to allow querying movies by category and year. You'd use this data structure:
<pre class="lang-js prettyprint-override"><code>&quot;movie1&quot;: {
 &quot;genre&quot;: &quot;comedy&quot;,
 &quot;name&quot;: &quot;As good as it gets&quot;,
 &quot;lead&quot;: &quot;Jack Nicholson&quot;,
 &quot;genre_year&quot;: &quot;comedy_1997&quot;
}, //...
</code></pre>
And then query for comedies of the 90s with:
<pre class="lang-js prettyprint-override"><code>ref
 .orderBy('genre_year')
 .startAt('comedy_1990')
 .endAt('comedy_2000')
 .on('child_added', function(snapshot) { 
 var movie = snapshot.val();
 console.log(movie);
 });
</code></pre>
If you need to filter on more than just the year, make sure to add the other date parts in descending order, e.g. <code>&quot;comedy_1997-12-25&quot;</code>. This way the lexicographical ordering that Firebase does on string values will be the same as the chronological ordering.
This combining of values in a property can work with more than two values, but you can only do a range filter on the last value in the composite property.
A very special variant of this is implemented by the <a href="https://github.com/firebase/geofire-js" rel="noreferrer">GeoFire library for Firebase</a>. This library combines the latitude and longitude of a location into a so-called <a href="https://en.wikipedia.org/wiki/Geohash" rel="noreferrer">Geohash</a>, which can then be used to do realtime range queries on Firebase.
<h3>3. create a custom index programmatically</h3>
Yet another alternative is to do what we've all done before this new Query API was added: create an index in a different node:
<pre class="lang-js prettyprint-override"><code> &quot;movies&quot;
 // the same structure you have today
 &quot;by_genre&quot;
 &quot;comedy&quot;
 &quot;by_lead&quot;
 &quot;Jack Nicholson&quot;
 &quot;movie1&quot;
 &quot;Jim Carrey&quot;
 &quot;movie3&quot;
 &quot;Horror&quot;
 &quot;by_lead&quot;
 &quot;Jack Nicholson&quot;
 &quot;movie2&quot;
 
</code></pre>
There are probably more approaches. For example, this answer highlights an alternative tree-shaped custom index: <a href="https://stackoverflow.com/a/34105063">https://stackoverflow.com/a/34105063</a>
<hr />
If none of these options work for you, but you still want to store your data in Firebase, you can also consider using its <a href="https://firebase.google.com/docs/firestore" rel="noreferrer">Cloud Firestore database</a>.
Cloud Firestore can handle multiple equality filters in a single query, but only one range filter. Under the hood it essentially uses the same query model, but it's like it auto-generates the composite properties for you. See Firestore's documentation on <a href="https://firebase.google.com/docs/firestore/query-data/queries#compound_queries" rel="noreferrer">compound queries</a>.

blocks|key|143701|text|var+ref+=+new+Firebase('https://your.firebaseio.com/');

Query+query+=+ref.orderByChild('genre').equalTo('comedy');
query.addValueEventListener(new+ValueEventListener()+{
++++@Override
++++public+void+onDataChange(DataSnapshot+dataSnapshot)+{
++++++++for+(DataSnapshot+movieSnapshot+:+dataSnapshot.getChildren())+{
++++++++++++Movie+movie+=+dataSnapshot.getValue(Movie.class);
++++++++++++if+(movie.getLead().equals('Jack+Nicholson'))+{
++++++++++++++++console.log(movieSnapshot.getKey());
++++++++++++}
++++++++}
++++}

++++@Override
++++public+void+onCancelled(FirebaseError+firebaseError)+{

++++}
});|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|143702|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var ref = new Firebase('https://your.firebaseio.com/');

Query query = ref.orderByChild('genre').equalTo('comedy');
query.addValueEventListener(new ValueEventListener() {
 @Override
 public void onDataChange(DataSnapshot dataSnapshot) {
 for (DataSnapshot movieSnapshot : dataSnapshot.getChildren()) {
 Movie movie = dataSnapshot.getValue(Movie.class);
 if (movie.getLead().equals('Jack Nicholson')) {
 console.log(movieSnapshot.getKey());
 }
 }
 }

 @Override
 public void onCancelled(FirebaseError firebaseError) {

 }
});
</code></pre>

blocks|key|145095|text|我已经编写了一个个人库，它允许您按多个值排序，所有的排序都在服务器上完成。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|145096|145097|Querybase接受一个Firebase数据库引用和一个您想要索引的字段数组。当您创建新记录时，它将自动处理允许多次查询的键的生成。需要注意的是，它只支持直接等价(不小于或大于)。|145098|const+databaseRef+=+firebase.database().ref().child('people');
const+querybaseRef+=+querybase.ref(databaseRef,+['name',+'age',+'location']);

//+Automatically+handles+composite+keys
querybaseRef.push({+
++name:+'David',
++age:+27,
++location:+'SF'
});

//+Find+records+by+multiple+fields
//+returns+a+Firebase+Database+ref
const+queriedDbRef+=+querybaseRef
+.where({
+++name:+'David',
+++age:+27
+});

//+Listen+for+realtime+updates
queriedDbRef.on('value',+snap+=>+console.log(snap));|code-block|syntax|javascript|145099|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|M|8|@]|9|@]|A|$]]|$1|C|3|D|5|6|7|N|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|O|8|@]|9|@]|A|$H|I]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

I've written a personal library that allows you to order by multiple values, with all the ordering done on the server.
<h3><a href="https://github.com/davideast/Querybase" rel="nofollow noreferrer">Meet Querybase!</a></h3>
Querybase takes in a Firebase Database Reference and an array of fields you wish to index on. When you create new records it will automatically handle the generation of keys that allow for multiple querying. The caveat is that it only supports straight equivalence (no less than or greater than).
<pre class="lang-js prettyprint-override"><code>const databaseRef = firebase.database().ref().child('people');
const querybaseRef = querybase.ref(databaseRef, ['name', 'age', 'location']);

// Automatically handles composite keys
querybaseRef.push({ 
 name: 'David',
 age: 27,
 location: 'SF'
});

// Find records by multiple fields
// returns a Firebase Database ref
const queriedDbRef = querybaseRef
 .where({
 name: 'David',
 age: 27
 });

// Listen for realtime updates
queriedDbRef.on('value', snap =&gt; console.log(snap));
</code></pre>

blocks|key|2934867|text|ref.orderByChild("lead").startAt("Jack+Nicholson").endAt("Jack+Nicholson").listner....|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2934868|这将会起作用。|unstyled|2934869|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>ref.orderByChild("lead").startAt("Jack Nicholson").endAt("Jack Nicholson").listner....
</code></pre>

This will work.

blocks|key|145144|text|Frank的回答是好的，但是Firestore最近引入了array-contains，这使得它更容易做和查询。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|145145|您可以创建一个filters字段来添加过滤器。您可以根据需要添加任意多个值。例如，要按喜剧和Jack+Nicholson过滤，您可以添加值comedy_Jack+Nicholson，但如果您还希望按comedy和2014筛选，则可以添加值comedy_2014，而无需创建更多字段。|145146|{
++"movies":+{
++++"movie1":+{
++++++"genre":+"comedy",
++++++"name":+"As+good+as+it+gets",
++++++"lead":+"Jack+Nicholson",
++++++"year":+2014,
++++++"filters":+[
++++++++"comedy_Jack+Nicholson",
++++++++"comedy_2014"
++++++]
++++}
++}
}|code-block|syntax|javascript|145147|entityMap|0|LINK|mutability|MUTABLE|url|https://firebase.google.com/docs/firestore/query-data/queries#array_membership^0|S|E|S|E|0|0|7|7|1X|L|3B|B|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Frank's answer is good but Firestore introduced <a href="https://firebase.google.com/docs/firestore/query-data/queries#array_membership" rel="nofollow noreferrer"><code>array-contains</code></a> recently that makes it easier to do AND queries.
You can create a <code>filters</code> field to add you filters. You can add as many values as you need. For example to filter by comedy and Jack Nicholson you can add the value <code>comedy_Jack Nicholson</code> but if you also you want to by comedy and 2014 you can add the value <code>comedy_2014</code> without creating more fields.
<pre class="lang-json prettyprint-override"><code>{
 &quot;movies&quot;: {
 &quot;movie1&quot;: {
 &quot;genre&quot;: &quot;comedy&quot;,
 &quot;name&quot;: &quot;As good as it gets&quot;,
 &quot;lead&quot;: &quot;Jack Nicholson&quot;,
 &quot;year&quot;: 2014,
 &quot;filters&quot;: [
 &quot;comedy_Jack Nicholson&quot;,
 &quot;comedy_2014&quot;
 ]
 }
 }
}
</code></pre>

blocks|key|2722764|text|Firebase不允许查询多个条件。然而，我确实找到了解决这个问题的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2722765|我们需要从数据库下载初始过滤数据，并将其存储在数组列表中。|offset|length|style|BOLD|2722766|++++++++++++++++Query+query+=+databaseReference.orderByChild("genre").equalTo("comedy");
++++++++++++++++databaseReference.addValueEventListener(new+ValueEventListener()+{
++++++++++++++++++++@Override
++++++++++++++++++++public+void+onDataChange(@NonNull+DataSnapshot+dataSnapshot)+{

++++++++++++++++++++++++ArrayList<Movie>+movies+=+new+ArrayList<>();
++++++++++++++++++++++++for+(DataSnapshot+dataSnapshot1+:+dataSnapshot.getChildren())+{
++++++++++++++++++++++++++++String+lead+=+dataSnapshot1.child("lead").getValue(String.class);
++++++++++++++++++++++++++++String+genre+=+dataSnapshot1.child("genre").getValue(String.class);

++++++++++++++++++++++++++++movie+=+new+Movie(lead,+genre);

++++++++++++++++++++++++++++movies.add(movie);

++++++++++++++++++++++++}

++++++++++++++++++++++++filterResults(movies,+"Jack+Nicholson");

++++++++++++++++++++++++}

++++++++++++++++++++}

++++++++++++++++++++@Override
++++++++++++++++++++public+void+onCancelled(@NonNull+DatabaseError+databaseError)+{

++++++++++++++++++++}
++++++++++++++++});|code-block|syntax|javascript|2722767|一旦我们从数据库中获得了初始过滤数据，我们就需要在后端进行进一步的过滤。|2722768|public+void+filterResults(final+List<Movie>+list,++final+String+genre)+{
++++++++List<Movie>+movies+=+new+ArrayList<>();
++++++++movies+=+list.stream().filter(o+->+o.getLead().equals(genre)).collect(Collectors.toList());
++++++++System.out.println(movies);

++++++++employees.forEach(movie+->+System.out.println(movie.getFirstName()));
++++}|2722769|entityMap^0|0|0|T|0|0|0|10|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|O|3|P|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

Firebase doesn't allow querying with multiple conditions. 
However, I did find a way around for this:

We need to download the initial filtered data from the database and store it in an array list.

<pre><code> Query query = databaseReference.orderByChild("genre").equalTo("comedy");
 databaseReference.addValueEventListener(new ValueEventListener() {
 @Override
 public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

 ArrayList&lt;Movie&gt; movies = new ArrayList&lt;&gt;();
 for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
 String lead = dataSnapshot1.child("lead").getValue(String.class);
 String genre = dataSnapshot1.child("genre").getValue(String.class);

 movie = new Movie(lead, genre);

 movies.add(movie);

 }

 filterResults(movies, "Jack Nicholson");

 }

 }

 @Override
 public void onCancelled(@NonNull DatabaseError databaseError) {

 }
 });
</code></pre>

Once we obtain the initial filtered data from the database, we need to do further filter in our backend.

<pre><code>public void filterResults(final List&lt;Movie&gt; list, final String genre) {
 List&lt;Movie&gt; movies = new ArrayList&lt;&gt;();
 movies = list.stream().filter(o -&gt; o.getLead().equals(genre)).collect(Collectors.toList());
 System.out.println(movies);

 employees.forEach(movie -&gt; System.out.println(movie.getFirstName()));
 }
</code></pre>

blocks|key|143776|text|来自firebase实时数据库的数据为_InternalLinkedHashMap。你也可以很容易地把它转换成你的地图和查询。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143777|例如，我有一个聊天应用程序，我使用实时数据库来存储用户的uid和布尔值，而不管用户是否在线。如下图所示。|143778|​|143779|📷|atomic|offset|length|143780|143781|现在，我有了一个类RealtimeDatabase和一个静态方法getAllUsersOnineStatus()。|143782|static+getOnilineUsersUID()+{
var+dbRef+=+FirebaseDatabase.instance;
DatabaseReference+reference+=+dbRef.reference().child("Online");
reference.once().then((value)+{
++Map<String,+bool>+map+=+Map<String,+bool>.from(value.value);
++List+users+=+[];
++map.forEach((key,+value)+{
++++if+(value)+{
++++++users.add(key);
++++}
++});
++print(users);
});|code-block|syntax|javascript|143783|}|143784|它将打印NOraDTGaQSZbIEszidCujw1AEym2|143785|我是flutter的新手，如果你知道更多，请更新答案。|143786|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/206e52a9ce3f42fb3230ecc9d92fd94c.png|imageAlt^0|0|0|0|0|1|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|18|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|19|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|1A|8|@]|9|@$I|1B|J|1C|1|1D]]|A|$]]|$1|K|3|E|5|6|7|1E|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1F|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1G|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1H|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1I|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1J|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15|16|-4]]]]

The data from firebase realtime database is as _InternalLinkedHashMap&lt;dynamic, dynamic&gt;.
You can also just convert this it to your map and query very easily.
For example, I have a chat app and I use realtime database to store the uid of the user and the bool value whether the user is online or not. As the picture below.
<a href="https://i.stack.imgur.com/3WK64.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3WK64.png" alt="" /></a>
Now, I have a class RealtimeDatabase and a static method getAllUsersOnineStatus().
<pre><code>static getOnilineUsersUID() {
var dbRef = FirebaseDatabase.instance;
DatabaseReference reference = dbRef.reference().child(&quot;Online&quot;);
reference.once().then((value) {
 Map&lt;String, bool&gt; map = Map&lt;String, bool&gt;.from(value.value);
 List users = [];
 map.forEach((key, value) {
 if (value) {
 users.add(key);
 }
 });
 print(users);
});
</code></pre>
}
It will print [NOraDTGaQSZbIEszidCujw1AEym2]
I am new to flutter If you know more please update the answer.

blocks|key|145183|text|对于Cloud+Firestore|type|unstyled|depth|inlineStyleRanges|entityRanges|data|145184|https://firebase.google.com/docs/firestore/query-data/queries#compound_queries|offset|length|145185|复合查询您可以链接多个相等运算符(==或数组-包含)方法，以创建更具体的查询(逻辑AND)。但是，您必须创建一个复合索引来将相等运算符与不等运算符<、<=、>和!=组合在一起。|145186|citiesRef.where('state'，'=='，'CO').where('name'，'=='，'Denver')；citiesRef.where('state'，'=='，'CA').where('population'，'<'，‘1000000)；只能对单个字段进行range+(<，<=，>，>=)或not+equals+(!=)比较，复合查询中最多只能包含一个array-contains或array-contains-any子句：|145187|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|26|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@$D|S|E|T|1|U]]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|C]]]]

For Cloud Firestore
<a href="https://firebase.google.com/docs/firestore/query-data/queries#compound_queries" rel="nofollow noreferrer">https://firebase.google.com/docs/firestore/query-data/queries#compound_queries</a>
Compound queries
You can chain multiple equality operators (== or array-contains) methods to create more specific queries (logical AND). However, you must create a composite index to combine equality operators with the inequality operators, &lt;, &lt;=, &gt;, and !=.
citiesRef.where('state', '==', 'CO').where('name', '==', 'Denver');
citiesRef.where('state', '==', 'CA').where('population', '&lt;', 1000000);
You can perform range (&lt;, &lt;=, &gt;, &gt;=) or not equals (!=) comparisons only on a single field, and you can include at most one array-contains or array-contains-any clause in a compound query:

<pre class="lang-json prettyprint-override"><code>{
 &quot;movies&quot;: {
 &quot;movie1&quot;: {
 &quot;genre&quot;: &quot;comedy&quot;,
 &quot;name&quot;: &quot;As good as it gets&quot;,
 &quot;lead&quot;: &quot;Jack Nicholson&quot;
 },
 &quot;movie2&quot;: {
 &quot;genre&quot;: &quot;Horror&quot;,
 &quot;name&quot;: &quot;The Shining&quot;,
 &quot;lead&quot;: &quot;Jack Nicholson&quot;
 },
 &quot;movie3&quot;: {
 &quot;genre&quot;: &quot;comedy&quot;,
 &quot;name&quot;: &quot;The Mask&quot;,
 &quot;lead&quot;: &quot;Jim Carrey&quot;
 }
 }
}
</code></pre>
I am a Firebase newbie. How can I retrieve a result from the data above where <code>genre = 'comedy'</code> AND <code>lead = 'Jack Nicholson'</code>?
What options do I have?

Query based on multiple where clauses in Firebase

{  "movies": {    "movie1": {      "genre": "comedy",      "name": "As good as it gets",      "lead": "Jack Nicholson"    },    "movie2": {      "genre": "Horro...

问Firebase中基于多where子句的查询
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