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()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));

Web

citiesRef.orderBy("name").limit(3);
Swift
注意:這項產品不適用於 watchOS 和 App Clip 目標。
citiesRef.order(by: "name").limit(to: 3)
Objective-C
注意:這項產品不適用於 watchOS 和 App Clip 目標。
[[citiesRef queryOrderedByField:@"name"] queryLimitedTo:3];

Kotlin+KTX

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

Java

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

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("name").limit(3);
Java
Query query = cities.orderBy("name").limit(3);
Query query = cities.orderBy("name").limitToLast(3);
Python
cities_ref = db.collection("cities")
query = cities_ref.order_by("name").limit_to_last(2)
results = query.get()

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name").limit_to_last(2)
results = await query.get()
C++
cities_ref.OrderBy("name").Limit(3);
Node.js
const firstThreeRes = await citiesRef.orderBy('name').limit(3).get();
Go
query := cities.OrderBy("name", firestore.Asc).Limit(3)
query := cities.OrderBy("name", firestore.Asc).LimitToLast(3)
PHP

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);
Unity
Query query = citiesRef.OrderBy("Name").Limit(3);
C#
Query query = citiesRef.OrderBy("Name").Limit(3);
Ruby
query = cities_ref.order("name").limit(3)

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));

Web

citiesRef.orderBy("name", "desc").limit(3);
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)
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];

Kotlin+KTX

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

Java

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

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("name", descending: true).limit(3);
Java
Query query = cities.orderBy("name", Direction.DESCENDING).limit(3);
Python
cities_ref = db.collection("cities")
query = cities_ref.order_by("name", direction=firestore.Query.DESCENDING).limit(3)
results = query.stream()

Python

cities_ref = db.collection("cities")
query = cities_ref.order_by("name", direction=firestore.Query.DESCENDING).limit(3)
results = query.stream()
C++
cities_ref.OrderBy("name", Query::Direction::kDescending).Limit(3);
Node.js
const lastThreeRes = await citiesRef.orderBy('name', 'desc').limit(3).get();
Go
query := cities.OrderBy("name", firestore.Desc).Limit(3)
PHP

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);
Unity
Query query = citiesRef.OrderByDescending("Name").Limit(3);
C#
Query query = citiesRef.OrderByDescending("Name").Limit(3);
Ruby
query = cities_ref.order("name", "desc").limit(3)

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"));

Web

citiesRef.orderBy("state").orderBy("population", "desc");
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)
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];

Kotlin+KTX

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

Java

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

Dart

final citiesRef = db.collection("cities");
citiesRef.orderBy("state").orderBy("population", descending: true);
Java
Query query = cities.orderBy("state").orderBy("population", Direction.DESCENDING);
Python
cities_ref = db.collection("cities")
ordered_city_ref = cities_ref.order_by("state").order_by(
    "population", direction=firestore.Query.DESCENDING
)

Python

cities_ref = db.collection("cities")
cities_ref.order_by("state").order_by(
    "population", direction=firestore.Query.DESCENDING
)
C++
cities_ref.OrderBy("state").OrderBy("name", Query::Direction::kDescending);
Node.js
const byStateByPopRes = await citiesRef.orderBy('state').orderBy('population', 'desc').get();
Go
query := client.Collection("cities").OrderBy("state", firestore.Asc).OrderBy("population", firestore.Desc)
PHP

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');
Unity
Query query = citiesRef.OrderBy("State").OrderByDescending("Population");
C#
Query query = citiesRef.OrderBy("State").OrderByDescending("Population");
Ruby
query = cities_ref.order("state").order("population", "desc")

您可以將 where() 篩選器與 orderBy()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));

Web

citiesRef.where("population", ">", 100000).orderBy("population").limit(2);
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)
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];

Kotlin+KTX

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

Java

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

Dart

final citiesRef = db.collection("cities");
citiesRef
    .where("population", isGreaterThan: 100000)
    .orderBy("population")
    .limit(2);
Java
Query query = cities.whereGreaterThan("population", 2500000L).orderBy("population").limit(2);
Python
cities_ref = db.collection("cities")
query = (
    cities_ref.where(filter=FieldFilter("population", ">", 2500000))
    .order_by("population")
    .limit(2)
)
results = query.stream()

Python

cities_ref = db.collection("cities")
query = (
    cities_ref.where(filter=FieldFilter("population", ">", 2500000))
    .order_by("population")
    .limit(2)
)
results = query.stream()
C++
cities_ref.WhereGreaterThan("population", FieldValue::Integer(100000))
    .OrderBy("population")
    .Limit(2);
Node.js
const biggestRes = await citiesRef.where('population', '>', 2500000)
  .orderBy('population').limit(2).get();
Go
query := cities.Where("population", ">", 2500000).OrderBy("population", firestore.Desc).Limit(2)
PHP

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);
Unity
Query query = citiesRef
    .WhereGreaterThan("Population", 2500000)
    .OrderBy("Population")
    .Limit(2);
C#
Query query = citiesRef
    .WhereGreaterThan("Population", 2500000)
    .OrderBy("Population")
    .Limit(2);
Ruby
query = cities_ref.where("population", ">", 2_500_000).order("population").limit(2)

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);