Read Documents with VS Code使用VS Code读取文档

Prerequisites先决条件

If you have not done so already, you must complete the following prerequisites before you can read documents with a MongoDB Playground:如果您还没有这样做，则必须完成以下先决条件，然后才能使用MongoDB游乐场阅读文档：

• Create a connection to a MongoDB deployment.创建与MongoDB部署的连接。
• Activate the connection to the MongoDB deployment.激活与MongoDB部署的连接。
• Open a MongoDB Playground.打开一个MongoDB游乐场。
• Create Documents with VS Code使用VS Code创建文档 or create documents in a collection using a different method.或者使用不同的方法在集合中创建文档。

Read One Document阅读一个文档

To read one document, use the following syntax in your Playground:要阅读一个文档，请在游乐场中使用以下语法：

db.collection.findOne(
   { <query> },
   { <projection> }
)

If multiple documents satisfy the query, this method returns the first document according to the natural order which reflects the order of documents on the disk.如果多个文档满足查询，则此方法根据反映磁盘上文档顺序的自然顺序返回第一个文档。

To learn more about this method's parameters, see findOne() in the MongoDB Manual.要了解有关此方法参数的更多信息，请参阅MongoDB手册中的findOne()。

To run your Playground, press the Play Button at the top right of the Playground View. VS Code Extension splits your Playground and outputs the results of your Playground in the Playground Results.json pane. If you disabled split-view, VS Code Extension outputs the results of your Playground in a new tab.要运行游乐场，请按游乐场视图右上角的“播放”按钮。VS Code扩展拆分游乐场，并在“游乐场Results.json”窗格中输出游乐场的结果。如果禁用拆分视图，VS Code扩展将在新选项卡中输出游乐场的结果。

You may edit any JSON document returned from a findOne() or find() operation.您可以编辑从findOne()或find()操作返回的任何JSON文档。

1. At the top of this document, click Edit Document. VS Code Extension opens it as an editable EJSON document titled <database>.<collection>:"<_id>".json.在此文档顶部，单击“编辑文档”。VS Code扩展将其作为标题为<database>.<collection>:"<_id>".json的可编辑EJSON文档打开。
2. Make any edits you require.根据需要进行任何编辑。

3. Press Ctrl + S (Windows/Linux) or Cmd + S to save the edited document to the MongoDB database.按Ctrl+S（Windows/Linux）或Cmd+S将编辑后的文档保存到MongoDB数据库。

   • If the update succeeds, VS Code Extension confirms that the database has stored the change.如果更新成功，VS Code扩展将确认数据库已存储更改。
   • If the update results in an error, VS Code Extension displays it.如果更新导致错误，VS Code扩展将显示它。

use("test");

db.sales.findOne(
  { "_id" : 1 },
  { "_id" : 0 }
);

{
  item: 'abc',
  price: 10,
  quantity: 2,
  date: 2014-03-01T08:00:00.000Z
}

Read Many Documents阅读许多文档

To read many documents, use the following syntax in your Playground:要阅读许多文档，请在游乐场中使用以下语法：

db.collection.find(
   { <query> },
   { <projection> }
)

For a detailed description of this method's parameters, see find() in the MongoDB Manual.有关此方法参数的详细说明，请参阅MongoDB手册中的find()。

To run your Playground, press the Play Button at the top right of the Playground View. VS Code Extension splits your Playground and outputs the results of your Playground in the Playground Results.json pane. If you disabled split-view, VS Code Extension outputs the results of your Playground in a new tab.要运行游乐场，请按游乐场视图右上角的“播放按钮”。VS Code扩展拆分游乐场，并在“游乐场Results.json”窗格中输出游乐场的结果。如果禁用拆分视图，VS Code扩展将在新选项卡中输出游乐场的结果。

use("test");

db.sales.find(
  { "item" : "abc" },
  { "price" : 1 }
);

[
  {
    _id: 2,
    price: 10
  },
  {
    _id: 6,
    price: 10
  },
  {
    _id: 9,
    price: 10
  },
  {
    _id: 1,
    price: 10
  }
]

Read Documents with a Cursor使用游标读取文档

In VS Code, cursors automatically log up to 20 documents by default. If there are more results, you can access them using the cursor's iteration methods or convert the cursor to an array.在VS Code中，默认情况下游标会自动记录多达20个文档。如果有更多结果，您可以使用游标的迭代方法访问它们，或者将游标转换为数组。

To convert an entire cursor to an array, use the following syntax in your Playground:要将整个游标转换为数组，请在游乐场中使用以下语法：

let cursor = db.collection.find({ <query> });

cursor.toArray();

use("test");

let cursor = db.sales.find(
  { "price": { $gte: 10 } },
  { "price": 1 }
);

cursor.toArray();

[
   {
      "_id": 2,
      "price": 10
   },
   {
      "_id": 3,
      "price": 20
   },
   {
      "_id": 6,
      "price": 10
   },
   {
      "_id": 9,
      "price": 10
   }
]

Learn More了解更多

For more detailed documentation on cursor methods and behaviors, see:有关游标方法和行为的更多详细文档，请参阅：

• MongoDB Cursors OverviewMongoDB Cursors概述
• Iterate a Cursor迭代游标