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排序及限制資料

Firestore 提供強大的查詢功能，可指定要從集合中擷取的檔案。如「取得資料」一文所述，這些查詢也可以搭配 get() 或 addSnapshotListener() 使用。

排序及限制資料

根據預設，查詢會擷取所有符合查詢條件的文件，並依文件 ID 遞增排序。您可以使用 orderBy() 指定資料的排序順序，並使用 limit() 限制擷取的檔案數量。如要指定 limit()，值必須大於或等於零。

舉例來說，您可以查詢前 3 個依字母順序排列的城市：

網頁版 9

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

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

網頁版 8

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
Android

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

Java
Android

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
(Async)

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

如要向 Firestore 進行驗證，請設定應用程式預設憑證。詳情請參閱「為本機開發環境設定驗證」。

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

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

你也可以依遞減順序排序，取得最後 3 個城市：

網頁版 9

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

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

網頁版 8

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
Android

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

Java
Android

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
(Async)

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

如要向 Firestore 進行驗證，請設定應用程式預設憑證。詳情請參閱「為本機開發環境設定驗證」。

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

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，假設您想依州別排序，並在每個州別中依人口數遞減排序：

網頁版 9

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

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

網頁版 8

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
Android

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

Java
Android

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
(Async)

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

如要向 Firestore 進行驗證，請設定應用程式預設憑證。詳情請參閱「為本機開發環境設定驗證」。

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

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() 結合使用。在下列範例中，查詢會定義人口數門檻、依人口數遞增排序，並只傳回超過門檻的前幾筆結果：

網頁版 9

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

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

網頁版 8

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
Android

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

Java
Android

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
(Async)

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

如要向 Firestore 進行驗證，請設定應用程式預設憑證。詳情請參閱「為本機開發環境設定驗證」。

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

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，如果篩選器包含範圍比較 (<、<=、>、>=)，則第一個排序必須使用相同欄位，請參閱下方的 orderBy() 限制清單。

限制

請注意，orderBy() 子句有下列限制：

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

`orderBy` 和存在

依指定欄位排序查詢時，查詢只能傳回排序依據欄位存在的文件。

舉例來說，即使文件符合查詢篩選條件，如果未設定 population 欄位，下列查詢也不會傳回任何文件。

Java

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

相關效果適用於不等式。如果查詢在欄位上使用不等式篩選器，也表示要依該欄位排序。即使文件中包含 country = USA，下列查詢也不會傳回沒有 population 欄位的文件。如要解決這個問題，您可以針對每個排序執行個別查詢，也可以為所有排序依據的欄位指派值。

Java

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

上述查詢包含不等式上的隱含 order-by，等同於下列查詢：

Java

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

排序及限制資料

排序及限制資料

網頁版 9

網頁版 8

Swift

Objective-C

KotlinAndroid

JavaAndroid

Dart

Java

Python

Python(Async)

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

網頁版 9

網頁版 8

Swift

Objective-C

KotlinAndroid

JavaAndroid

Dart

Java

Python

Python(Async)

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

網頁版 9

網頁版 8

Swift

Objective-C

KotlinAndroid

JavaAndroid

Dart

Java

Python

Python(Async)

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

網頁版 9

網頁版 8

Swift

Objective-C

KotlinAndroid

JavaAndroid

Dart

Java

Python

Python(Async)

C++

Node.js

Go

PHP

PHP

Unity

C#

Ruby

限制

orderBy 和存在

Java

Java

Java

Kotlin
Android

Java
Android

Python
(Async)

Kotlin
Android

Java
Android

Python
(Async)

Kotlin
Android

Java
Android

Python
(Async)

Kotlin
Android

Java
Android

Python
(Async)

`orderBy` 和存在