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Find Multiple Documents查找多个文档

You can query for multiple documents in a collection with collection.find(). 您可以使用collection.find()查询集合中的多个文档。The find() method uses a query document that you provide to match the subset of the documents in the collection that match the query. find()方法使用您提供的查询文档来匹配集合中与查询匹配的文档子集。If you don't provide a query document (or if you provide an empty document), MongoDB returns all documents in the collection. 如果您没有提供查询文档（或者提供了一个空文档），MongoDB将返回集合中的所有文档。For more information on querying MongoDB, see our documentation on query documents.有关查询MongoDB的更多信息，请参阅我们关于查询文档的文档。

You can also define additional query options such as sort and projection to configure the result set. 您还可以定义其他查询选项，如排序和投影，以配置结果集。You can specify these in the options parameter in your find() method call in sort and projection objects. 您可以在find()方法的options参数中指定sort和projection对象。See collection.find() for more information on the parameters you can pass to the method.有关可以传递给方法的参数的更多信息，请参阅collection.find()。

The find() method returns a FindCursor that manages the results of your query. find()方法返回一个管理查询结果的FindCursor。You can iterate through the matching documents using the for await...of syntax, or one of the following cursor methods:您可以使用for await...of语法来遍历匹配的文档，或以下游标方法之一：

  • next()
  • toArray()

If no documents match the query, find() returns an empty cursor.如果没有与查询匹配的文档，find()将返回一个空游标。

Example实例

The following snippet finds documents from the movies collection. 以下片段查找movies集合中的文档。It uses the following parameters:它使用以下参数：

  • A query document that configures the query to return only movies with a runtime of less than 15 minutes.将查询配置为仅返回运行时间小于15分钟的电影的查询文档。
  • A sort that organizes returned documents in ascending order by title (alphabetical order in which "A" comes before "Z" and "1" before "9").一种按标题升序组织返回文档的排序（按字母顺序，“A”在“Z”之前，“1”在“9”之前）。
  • A projection that explicitly excludes the _id field from returned documents and explicitly includes only the title and imdb object (and its embedded fields).一个投影，它从返回的文档中显式地排除_id字段，并显式地只包括title和imdb对象（及其嵌入的字段）。
Note

You can use this example to connect to an instance of MongoDB and interact with a database that contains sample data. 您可以使用此示例连接到MongoDB的实例，并与包含示例数据的数据库进行交互。To learn more about connecting to your MongoDB instance and loading a sample dataset, see the Usage Examples guide.要了解有关连接到MongoDB实例和加载示例数据集的更多信息，请参阅用法实例指南。

import { MongoClient } from "mongodb";

// Replace the uri string with your MongoDB deployment's connection string.将uri字符串替换为MongoDB部署的连接字符串。
const uri = "<connection string uri>";

const client = new MongoClient(uri);

async function run() {
  try {
    const database = client.db("sample_mflix");
    const movies = database.collection("movies");

    // query for movies that have a runtime less than 15 minutes查询运行时间小于15分钟的电影
    const query = { runtime: { $lt: 15 } };

    const options = {
      // sort returned documents in ascending order by title (A->Z)按标题升序对返回的文档进行排序（A->Z）
      sort: { title: 1 },
      // Include only the `title` and `imdb` fields in each returned document在每个返回的文档中只包括“title”和“imdb”字段
      projection: { _id: 0, title: 1, imdb: 1 },
    };

    const cursor = movies.find(query, options);

    // print a message if no documents were found如果找不到文档，则打印消息
    if ((await movies.countDocuments(query)) === 0) {
      console.log("No documents found!");
    }

    for await (const doc of cursor) {
      console.dir(doc);
    }

  } finally {
    await client.close();
  }
}
run().catch(console.dir);

If you run the preceding example, you should see the following output:如果运行前面的示例，您应该会看到以下输出：

{ title: '10 Minutes', imdb: { rating: 7.9, votes: 743, id: 339976 } }
{ title: '3x3', imdb: { rating: 6.9, votes: 206, id: 1654725 } }
{ title: '7:35 in the Morning', imdb: { rating: 7.3, votes: 1555, id: 406501 } }
{ title: '8', imdb: { rating: 7.8, votes: 883, id: 1592502 } }
...

The sort and projection options can also be specified as methods (sort() and project(), respectively) chained to the find() method. sort和projection选项也可以指定为链接到find()方法的方法（分别为sort()和project()）。The following two commands are equivalent:以下两个命令是等效的：

movies.find({ runtime: { $lt: 15 } }, { sort: { title: 1 }, projection: { _id: 0, title: 1, imdb: 1 }});
movies.find({ runtime: { $lt: 15 } }).sort({ title: 1}).project({ _id: 0, title: 1, imdb: 1 });