Databases and Collections

Overview

In this guide, you can learn how to interact with MongoDB databases and collections by using the Node.js driver.

MongoDB organizes data into a hierarchy of the following levels:

• Databases: Top-level data structures in a MongoDB deployment that store collections.

• Collections: Groups of MongoDB documents. They are analogous to tables in relational databases.

• Documents: Units that store literal data such as strings, numbers, dates, and other embedded documents. For more information about document field types and structure, see the Documents entry in the MongoDB Server manual.

Access a Database

You can access a database by calling the db() method on a MongoClient instance.

The following example accesses a database named "test_database":

const database = client.db("test_database");

Access a Collection

You can access a collection by calling the collection() method on a Db instance.

The following example accesses a collection named "test_collection":

const collection = database.collection("test_collection");

Create a Collection

To explicitly create a collection, call the createCollection() method on a Db instance.

The following example creates a collection named "example_collection":

const createColl = await database.createCollection("example_collection");

You can specify collection options, such as maximum size and document validation rules, by passing a CreateCollectionOptions instance to the createCollection() method. For a full list of optional parameters, see the create command entry in the MongoDB Server manual.

Get a List of Collections

You can query for a list of collections in a database by calling the listCollections() method on a Db instance.

The following example lists all collections in a database:

const colls = database.listCollections();
for await (const doc of colls) {
  console.log(doc)
}

{
  name: 'example_collection',
  type: 'collection',
  options: {},
  info: {
      readOnly: false,
      uuid: new UUID('...')
  },
  idIndex: { v: 2, key: { _id: 1 }, name: '_id_' }
}
{
  name: 'test_collection',
  type: 'collection',
  options: {},
  info: {
      readOnly: false,
      uuid: new UUID('...')
  },
  idIndex: { v: 2, key: { _id: 1 }, name: '_id_' }
}

To query for only the names of the collections in the database, pass the nameOnly option to the listCollections() method and set its value to true, as shown in the following code:

const names = database.listCollections({}, { nameOnly: true });
for await (const doc of names) {
  console.log(doc)
}

{ name: 'example_collection', type: 'collection' }
{ name: 'test_collection', type: 'collection' }

Delete a Collection

You can delete a collection by calling the drop() method on a Collection instance.

The following example deletes the "test_collection" collection:

const collectionToDelete = database.collection("test_collection");
await collectionToDelete.drop();

API Documentation

To learn more about any of the types or methods discussed in this guide, see the following API documentation:

• MongoClient

• Db

• Collection

• db()

• collection()

• createCollection()

• listCollections()

• dropCollection()