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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哪些文件。這些查詢也可以與 get() 或 addSnapshotListener() 搭配使用，如取得資料中所述。

訂單和限制資料

根據預設，查詢會依照文件 ID，以遞增順序擷取符合查詢的所有文件。您可以使用 orderBy() 指定資料的排序順序，以及限制使用 limit() 擷取的文件數量。如果指定 limit()，值必須大於或等於零。

舉例來說，您可以使用下列語法，按字母順序查詢前 3 個城市：

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

小茹敬上

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

小茹敬上

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

您也可以依多個欄位排序。例如，如果您想要依狀態排序，並在各狀態順序中按母體遞減排序：

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

小茹敬上

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。在以下範例中，查詢會定義母體門檻、按照人口遞增排序，然後只傳回超過門檻的前幾個結果：

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

小茹敬上

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 (<、<=、>、>=)，您的第一筆排序必須位於相同欄位，請參閱下方的 orderBy() 限制清單。

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

如果您按照特定欄位對查詢進行排序，查詢只能傳回「排序依據」欄位存在的文件。

舉例來說，下列查詢不會傳回未設定 population 欄位的任何文件，即使這些文件符合查詢篩選條件也一樣。

Java

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

相關效應適用於不等式。對欄位使用不等式篩選條件的查詢，也意味著依照該欄位排序。即使該文件中有 country = USA，下列查詢也不會傳回不含 population 欄位的文件。解決方法是，您可以針對每個排序執行個別查詢，或是為排序的所有欄位指派值。

Java

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

上述查詢包含不等式的隱含順序，且與下列條件相同：

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#

小茹敬上

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

小茹敬上

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

小茹敬上

Web

Web

Swift

Objective-C

Kotlin+KTX

Java

Dart

Java

Python

Python

C++

Node.js

Go

PHP

PHP

Unity

C#

小茹敬上

限制

orderBy和存在

Java

Java

Java

`orderBy`和存在