Adding Documents to MongoDB: The insertOne() Method

Learn how to efficiently add single documents to MongoDB collections using the insertOne() method. This guide will provide you with the necessary knowledge and examples to effectively populate your MongoDB databases with individual documents.

MongoDB - Insert Single Document in a Collection using insertOne()

In MongoDB, you can use various methods to insert documents into a collection:

• insertOne() - Inserts a single document.
• insert() - Inserts one or more documents.
• insertMany() - Inserts multiple documents.

Using insertOne()

The insertOne() method is used to insert a single document into a collection. The syntax is:

db.collection.insertOne(document, [writeConcern])
        

Parameters:

• document: The document to insert.
• writeConcern: Optional. Document expressing the write concern.

Example: Insert a Single Document

db.employees.insertOne({ 
    firstName: "John",
    lastName: "King",
    email: "john.king@abc.com"
})
        

Output:

{
  acknowledged: true,
  insertedId: ObjectId("616d44bea861820797edd9b0")
}
        

The insertOne() method returns an object with:

• acknowledged: Indicates if the operation was successful.
• insertedId: The unique identifier for the inserted document.

View Inserted Document in mongosh

db.employees.find().pretty()
        

Output:

{
    _id: ObjectId("616d44bea861820797edd9b0"),
    firstName: "John",
    lastName: "King",
    email: "john.king@abc.com"
}
        

Note: MongoDB does not enforce schemas, so you can insert documents with different fields into the same collection.

Inserting Documents with Custom _id

You can manually specify the _id field value:

db.employees.insertOne({ 
    _id: "1",
    firstName: "John",
    lastName: "King",
    email: "john.king@abc.com"
})
        

Output:

{
  acknowledged: true,
  insertedId: "1"
}
        

Ensure that the _id value is unique to avoid errors. Attempting to insert a document with a duplicate _id will result in an error:

db.employees.insertOne({ 
    _id: "1",
    firstName: "John",
    lastName: "King",
    email: "john.king@abc.com"
})
        

Output:

MongoServerError: E11000 duplicate key error collection: humanResourceDB.employees index: _id_ dup key: { _id: "1" }
        

Use the insertOne() method to insert documents into MongoDB collections, and manage custom _id values carefully to ensure uniqueness.