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透過 Cloud Firestore 排序及限制資料

Cloud Firestore 提供強大的查詢功能，可讓您指定要從集合擷取的文件。您也可以使用這些查詢搭配 get() 或 addSnapshotListener() 使用，方法如「取得資料：

訂單和限制資料

根據預設，查詢會擷取符合查詢的所有文件 (遞增排序查詢您可以使用 orderBy()，您可以使用 limit()。如果指定 limit()，值必須大於或等於設為零

舉例來說，你可以按字母順序查詢前 3 個城市取代為：

Web

import { query, orderBy, limit } from "firebase/firestore";  

const q = query(citiesRef, orderBy("name"), limit(3));order_and_limit.js

Web

citiesRef.orderBy("name").limit(3);test.firestore.js

Swift

注意：這項產品不適用於 watchOS 和 App Clip 目標。

citiesRef.order(by: "name").limit(to: 3)ViewController.swift

Objective-C

注意：這項產品不適用於 watchOS 和 App Clip 目標。

[[citiesRef queryOrderedByField:@"name"] queryLimitedTo:3];ViewController.m

Kotlin+KTX

citiesRef.orderBy("name").limit(3)DocSnippets.kt

Java

citiesRef.orderBy("name").limit(3);DocSnippets.java

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("name").limit(3);firestore.dart

Java

Query query = cities.orderBy("name").limit(3);
Query query = cities.orderBy("name").limitToLast(3);QueryDataSnippets.java

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name").limit_to_last(2)
results = query.get()snippets.py

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name").limit_to_last(2)
results = await query.get()snippets.py

C++

cities_ref.OrderBy("name").Limit(3);snippets.cpp

Node.js

const firstThreeRes = await citiesRef.orderBy('name').limit(3).get();index.js

Go

query := cities.OrderBy("name", firestore.Asc).Limit(3)
query := cities.OrderBy("name", firestore.Asc).LimitToLast(3)query.go

PHP

如要進一步瞭解如何安裝及建立 Cloud Firestore 用戶端，請參閱 Cloud Firestore 用戶端程式庫。

$query = $citiesRef->orderBy('name')->limit(3);query_order_limit.php

Unity

Query query = citiesRef.OrderBy("Name").Limit(3);

C#

Query query = citiesRef.OrderBy("Name").Limit(3);Program.cs

Ruby

query = cities_ref.order("name").limit(3)order_limit_data.rb

此外，您也可以遞減排序，取得「最近」3 個城市：

Web

import { query, orderBy, limit } from "firebase/firestore";  

const q = query(citiesRef, orderBy("name", "desc"), limit(3));order_and_limit_desc.js

Web

citiesRef.orderBy("name", "desc").limit(3);test.firestore.js

Swift

注意：這項產品不適用於 watchOS 和 App Clip 目標。

citiesRef.order(by: "name", descending: true).limit(to: 3)ViewController.swift

Objective-C

注意：這項產品不適用於 watchOS 和 App Clip 目標。

[[citiesRef queryOrderedByField:@"name" descending:YES] queryLimitedTo:3];ViewController.m

Kotlin+KTX

citiesRef.orderBy("name", Query.Direction.DESCENDING).limit(3)DocSnippets.kt

Java

citiesRef.orderBy("name", Direction.DESCENDING).limit(3);DocSnippets.java

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("name", descending: true).limit(3);firestore.dart

Java

Query query = cities.orderBy("name", Direction.DESCENDING).limit(3);QueryDataSnippets.java

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name", direction=firestore.Query.DESCENDING).limit(3)
results = query.stream()snippets.py

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name", direction=firestore.Query.DESCENDING).limit(3)
results = query.stream()snippets.py

C++

cities_ref.OrderBy("name", Query::Direction::kDescending).Limit(3);snippets.cpp

Node.js

const lastThreeRes = await citiesRef.orderBy('name', 'desc').limit(3).get();index.js

Go

query := cities.OrderBy("name", firestore.Desc).Limit(3)query.go

PHP

如要進一步瞭解如何安裝及建立 Cloud Firestore 用戶端，請參閱 Cloud Firestore 用戶端程式庫。

$query = $citiesRef->orderBy('name', 'DESC')->limit(3);query_order_desc_limit.php

Unity

Query query = citiesRef.OrderByDescending("Name").Limit(3);

C#

Query query = citiesRef.OrderByDescending("Name").Limit(3);Program.cs

Ruby

query = cities_ref.order("name", "desc").limit(3)order_limit_data.rb

您也可以依多個欄位排序。舉例來說，假設您要依據並按母體以遞減方式排序：

Web

import { query, orderBy } from "firebase/firestore";  

const q = query(citiesRef, orderBy("state"), orderBy("population", "desc"));order_multiple.js

Web

citiesRef.orderBy("state").orderBy("population", "desc");test.firestore.js

Swift

注意：這項產品不適用於 watchOS 和 App Clip 目標。

citiesRef
  .order(by: "state")
  .order(by: "population", descending: true)ViewController.swift

Objective-C

注意：這項產品不適用於 watchOS 和 App Clip 目標。

[[citiesRef queryOrderedByField:@"state"] queryOrderedByField:@"population" descending:YES];ViewController.m

Kotlin+KTX

citiesRef.orderBy("state").orderBy("population", Query.Direction.DESCENDING)DocSnippets.kt

Java

citiesRef.orderBy("state").orderBy("population", Direction.DESCENDING);DocSnippets.java

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("state").orderBy("population", descending: true);firestore.dart

Java

Query query = cities.orderBy("state").orderBy("population", Direction.DESCENDING);QueryDataSnippets.java

Python

cities_ref = db.collection("cities")
ordered_city_ref = cities_ref.order_by("state").order_by(
    "population", direction=firestore.Query.DESCENDING
)snippets.py

Python

cities_ref = db.collection("cities")
cities_ref.order_by("state").order_by(
    "population", direction=firestore.Query.DESCENDING
)snippets.py

C++

cities_ref.OrderBy("state").OrderBy("name", Query::Direction::kDescending);snippets.cpp

Node.js

const byStateByPopRes = await citiesRef.orderBy('state').orderBy('population', 'desc').get();index.js

Go

query := client.Collection("cities").OrderBy("state", firestore.Asc).OrderBy("population", firestore.Desc)query.go

PHP

如要進一步瞭解如何安裝及建立 Cloud Firestore 用戶端，請參閱 Cloud Firestore 用戶端程式庫。

$query = $citiesRef->orderBy('state')->orderBy('population', 'DESC');query_order_multi.php

Unity

Query query = citiesRef.OrderBy("State").OrderByDescending("Population");

C#

Query query = citiesRef.OrderBy("State").OrderByDescending("Population");Program.cs

Ruby

query = cities_ref.order("state").order("population", "desc")order_limit_data.rb

您可以將 where() 篩選器與 orderBy() 和 limit() 搭配使用。在下例，此查詢會定義母體門檻並按人口排序，並且只傳回超出門檻：

Web

import { query, where, orderBy, limit } from "firebase/firestore";  

const q = query(citiesRef, where("population", ">", 100000), orderBy("population"), limit(2));filter_and_order.js

Web

citiesRef.where("population", ">", 100000).orderBy("population").limit(2);test.firestore.js

Swift

注意：這項產品不適用於 watchOS 和 App Clip 目標。

citiesRef
  .whereField("population", isGreaterThan: 100000)
  .order(by: "population")
  .limit(to: 2)ViewController.swift

Objective-C

注意：這項產品不適用於 watchOS 和 App Clip 目標。

[[[citiesRef queryWhereField:@"population" isGreaterThan:@100000]
    queryOrderedByField:@"population"]
    queryLimitedTo:2];ViewController.m

Kotlin+KTX

citiesRef.whereGreaterThan("population", 100000).orderBy("population").limit(2)DocSnippets.kt

Java

citiesRef.whereGreaterThan("population", 100000).orderBy("population").limit(2);DocSnippets.java

Dart

final citiesRef = db.collection("cities");
citiesRef
    .where("population", isGreaterThan: 100000)
    .orderBy("population")
    .limit(2);firestore.dart

Java

Query query = cities.whereGreaterThan("population", 2500000L).orderBy("population").limit(2);QueryDataSnippets.java

Python

cities_ref = db.collection("cities")
query = (
    cities_ref.where(filter=FieldFilter("population", ">", 2500000))
    .order_by("population")
    .limit(2)
)
results = query.stream()snippets.py

Python

cities_ref = db.collection("cities")
query = (
    cities_ref.where(filter=FieldFilter("population", ">", 2500000))
    .order_by("population")
    .limit(2)
)
results = query.stream()snippets.py

C++

cities_ref.WhereGreaterThan("population", FieldValue::Integer(100000))
    .OrderBy("population")
    .Limit(2);snippets.cpp

Node.js

const biggestRes = await citiesRef.where('population', '>', 2500000)
  .orderBy('population').limit(2).get();index.js

Go

query := cities.Where("population", ">", 2500000).OrderBy("population", firestore.Desc).Limit(2)query.go

PHP

如要進一步瞭解如何安裝及建立 Cloud Firestore 用戶端，請參閱 Cloud Firestore 用戶端程式庫。

$query = $citiesRef
    ->where('population', '>', 2500000)
    ->orderBy('population')
    ->limit(2);query_order_limit_field_valid.php

Unity

Query query = citiesRef
    .WhereGreaterThan("Population", 2500000)
    .OrderBy("Population")
    .Limit(2);

C#

Query query = citiesRef
    .WhereGreaterThan("Population", 2500000)
    .OrderBy("Population")
    .Limit(2);Program.cs

Ruby

query = cities_ref.where("population", ">", 2_500_000).order("population").limit(2)order_limit_data.rb

不過，如果您的篩選器包含範圍比較 (<、<=、>、>=)，你的第一筆排序必須位於相同欄位，請參閱 orderBy() 清單相關限制。

限制

請注意，orderBy() 子句的下列限制：

orderBy() 子句也會篩選指定欄位是否存在。結果集將不會包含不含指定欄位的文件。

`orderBy`和存在

依特定欄位排序查詢時，該查詢只會傳回。

舉例來說，下列查詢不會傳回未設定「population」欄位，即使這些欄位在其他條件符合查詢篩選器也一樣。

Java

db.collection("cities").whereEqualTo("country", “USA”).orderBy(“population”);

相關效應適用於不等式。使用不等式篩選條件的查詢也會表示按照該欄位排序。下列查詢不會傳回不含 population 欄位的文件，如果文件包含 country = USA 標記。做為替代方案分別為每種排序查詢，您也可以為所有欄位指定值做為排序依據

Java

db.collection(“cities”).where(or(“country”, USA”), greaterThan(“population”, 250000));

上述查詢包含不相等的隱含順序，相當於以下程式碼：

Java

db.collection(“cities”).where(or(“country”, USA”), greaterThan(“population”, 250000)).orderBy(“population”);

透過 Cloud Firestore 排序及限制資料

訂單和限制資料

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

限制

orderBy和存在

Java

Java

Java

`orderBy`和存在